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fauxtog
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sooooooooo.  we have variable timing for the valves. supposedly 110 / 110, 115 / 115, and  ?100 / 110 ?
we have multiple cam grinds available like the stock one or the 104.
and we have multi distributors set ups like the 25D or the 45 with points or pertonix or....

I'm wondering what the performance benefit is for the different valve timing set ups. with the two different cams.  ie top end performance or low end torque or gas mileage or ease of driving.

I'm running the 104 grind on a higher compression piston 10:1 i think with stromberg carbs set  the valve timing at  115 / 115  and ign timing at 10 deg BTDC   recently switched from the 45 dist with points to my 25D with pertonix 

John H

btw i know this gets discussed and has been discussed but I never saw an answer to why 115 vs 110 especially with the higher lift cam and higher compression

ps any generous soul have a dellorto set up to spare?  ;)

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The 104 cams are supposed to use 104 pulleys.

I'll let someone more knowledgeable comment on the cam timing.

Kurt

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John H,

There was only one factory installed cam used in the Jensen-Healey...  the C-cam.   The various different valve timing values given in the manual are just a matter of timing that one cam to different MOP's (Maximum Opening Points).

The C-cam was designed to run at 110 IN / 110 EX MOP.   If you want your original equipment engine to run the best overall,  time both cams to 110 MOP.

When the original engines were going through pre-production testing,  they met the emissions standards of the day.   However, the new USA Federal emissions standards had been announced and were going to get more strict in 1974,  so JH/ Lotus chose to meet that coming standard from the beginning.   The test engines had passed the coming '74 Fed. standard,  but met the HC limit by such a narrow margin that it left no room for error or wear.   So they chose to tweak the engine a bit more before production.

Ignition timing and carburetion remained unchanged,  but both cams were re-timed to 115 MOP.   That retarded the intake 5°,  advanced the exhaust 5°,  for a total decrease in overlap of 10°  (from 52° to 42°).   That reduced the HC to a comfortable level,  but also reduced horsepower (about -10 Hp) and torque.   The engine was cleaner but weaker.   That's the set-up that went into the original J-H.

For 1975, the Fed's tighten the standard again.   Lotus backed way off on the ignition timing, leaned out the carbs and changed the cam timing to 100 IN / 110 EX.   The new cam timing went the other way,  "increasing the overlap" by 10° compared to 110/110, to 62°.   The extra overlap allowed the intake and exhaust gasses to co-mingle a bit longer.   The effect was like EGR (Exhaust Gas Recirculation), reducing the oxides of nitrogen.   The retarded ignition timing and lean carb mixture changes took care of the rest.

All together,  the changes pretty much castrated the 907,  and it didn't make enough torque to peal a grape.   One small upside of the 100/110 timing was that greater overlap favored high end horsepower;  unfortunately it did that at the further expense of low end torque.   As a result, they were able to advertise the same peak horsepower, and as we all know, horsepower sells cars.   However, the resulting "Torqueless Wonder" was not pleasant to drive in traffic, as it had to be rev'd hard to perform.

110 IN / 110 EX is the correct, as-designed C-cam timing.   100 and 115 are both emissions solutions that hurt performance in favor of lower emissions.   Again,  the 110/110 set up passed 1974 Federal emissions standards,  just not by a wide enough margin to make factory decision makers comfortable.   It's not a "dirty" setting,  and the engine runs the way it was meant to run..

If you have an original 100/110 engine,  re-time the cams to 110/110 MOP,  set the static ignition timing to around 14° BTDC,  and adjust the carb mixture for best running instead of setting it to produce a specified CO level at the tail pipe.

The 100° (rounded, really 97°),  110°  and 115°  MOP's are all present on the same, stock pulley.   Not all MOP's are marked on all part number versions of the pulley;  but dimensionally and functionally it's the same pulley.   The different MOP's are just a matter of how it's installed, flipped front to back, and indexed.

The stock pulleys canNOT be adjusted to produce the 104° MOP !!  New, dedicated pulleys are required for the 104° MOP.

Note that the 100° MOP, blue dot, single-MOP pulley is 100° MOP as marked; however, the blue dot on the 110/100 dual-MOP pulley is really 97° MOP. The math doesn't work out for 110° and 100° to both exist on one pulley, so Lotus cheated a bit with 97° MOP for the convenience of having both Red and Blue timing dots on one pulley. If you're just talking about it in conversation, then "100 MOP" or "blue-dot" works. However, if you're really timing the cams and trying to figure out the math of what's going on, then remember to use 97° as the working MOP for the blue dot on the dual-MOP, 110/100, red/blue pulley.

The 104 cam is a good street performance cam,  if street "performance" is what you want.   It will make more horsepower, and the engine will happily rev to redline and beyond.   But all that high end performance comes at a price in that the low end torque and drivability will suffer.   NOT A LOT, IMHO, but if you're one of those who is not pleased with the 907's low end performance,  then installing a pair of 104 cams will be a small step in the wrong direction.   I have a pair of 104's in an otherwise near-stock 907,  and I love 'em.   Different strokes for different folks.

The 104 cams require 104 MOP pulleys.   Don't run them at 110° MOP or you won't get what you paid for.   It's not wrong in a way that will bend valves or do something else that's potentially expensive to repair.   It's just not going to produce the good top end results you paid for... and it won't be the cam's fault.

The 104's high lift (0.410") will cause the stock valve springs to go coil-bound.   It's necessary to either cut the valve spring pocket a little deeper into the head,  or better yet, install a set of special, thin-wire valve springs.   Do not attempt to run a 104 cam with stock valve springs... something WILL break.

The "Three C's"  (Cams, Carbs, Compression) should always be changed in concert.    In order for a change to one to really produce it's greatest benefit,  the other's must also be changed appropriately at the same time.   Putting 104 cams on a stock, low compression 907 isn't going to produce the optimum results that give the 104 cams their performance reputation.    With a pair of 104 cams,  the compression should be 10:1 or higher,  and the carbs should be re-jetted.   Strombergs don't necessarily have to be replaced by Dellortos,  but new needles and jets should be installed.   Of course, Dellortos are the better companions for the 104 carbs.

If you install a pair of 104 cams in an otherwise stock Federal J-H 907,  you will get an increase in top end horsepower;  but you probably won't be as over-whelmed as you had hoped to be.   You’ll just end up being one more un-informed voice talking negative about the 104 cam when they really didn't do the cam justice during the installation.   Do it right, or don't complain later.

The 107 cams also require 104° MOP pulleys.   Starting from the stock C-cam as a benchmark,  the 107 goes the other way, milder compared to the 104 and stock cams.   The 104 has "hotter" valve timing, while the 107 has "milder" valve timing.   The 107 has 20° less duration;  however, the MOP change from 110 to 104 keeps the overlap in the same ball park.

The milder timing produces more low to mid-range torque, which really helps drivability around town.   Normally,  that would come at the expense of high end horsepower,  however, the 107 can also has:
1) significantly more lift, which helps the engine breathe better across the rev range, and...
2) very aggressive opening and closing ramps that result in more 'full open' time than with some 'hotter' cams.

The breathing gain due to greater lift, plus the aggressive way the valves are 'hammered' open and closed, offsets some of the expected top end power loss due to mild valve timing'. As a result, the upper rev range doesn't suffer 'as much' with this cam that favors low-end torque.

Peak horsepower is about the same,  but the improvement in low-end and mid-range torque is what makes the 107-cam engine 'feel' more powerful in commuter traffic.   There's a difference between power and torque, and many folk confuse them;  but the net effect is that the 107 helps the 907 feel stronger by making more low end torque.

In reality,  the 107 starts to run out of breath above 5500 rpm.   It will pull to redline, but not with the enthusiasm of the 104 cam. In contrast, a 104 cam will roar right up to redline with gusto, and scream right past it if you don't lift your right foot.

A pair of 107s was used in the 2.2 liter 912LC (Low Compression).   In that 'basic' 912 engine, the stroker crank really gives the engine's torque curve a significant boost.   Every 907 should get a 2.2 crank... IMHO, it's the best thing you can do for it.   Much of the 107 cam's reputation comes from the 91's stellar performance.   But much of the 912's torque really comes from the stroker crank.

The 107 cam will also help boost the 2.0 litre 907's low-end torque curve,  but don't get your expectations up to 912 levels if you keep the 2.0 crank.   IMHO,  the 107's reputation as the cure for all that ails the 907 is blown out of proportion and taken out of context from the 912 application.   It's beneficial for a commuter 907,  just don't get your expectations out of proportion.

One advantage the 107's milder timing gives it is that it's compatible with the stock 907 engine's lower compression (remember the three C's).   While a 104 cam really needs higher compression to perform at it's best, the 107 cam is at home with 8.4:1.   Plug-n-play.

*~*~*~*
The difference between the Lucas 23/25 and 43/45 distributors isn't significant, in terms of performance.   It's evolution,  new design,  new tooling.   The 43/45 is an improvement in terms of durability and more consistent timing.   And the larger diameter distributor cap spreads the terminals out a bit further, which makes it more resistant to arc'ing between terminals with higher voltage coils.   But in terms of timing and power output, there's no big advantage to either one.   If an older 23/25 distributor fails,  I would suggest putting your money into a 43/45 upgrade.   But don't switch expecting more horsepower.

The Pertronix Ignitor II is too large to fit in the 23/25, but it will fit in the 43/45. Being able to use the improved Ignitor II could be good justification for upgrading to the later distributors.

From a timing stand point,  the mechanical advance curve should be 16-18°,  all in by 2500 engine rpm (distributor rpm = 1/2 engine rpm).   Then set the static ignition timing to 12-16° BTDC, depending upon what local petrol will support.

*~*~**~
John H wrote:  I'm running the 104 grind on a higher compression piston 10:1 i think with stromberg carbs set  the valve timing at  115 / 115  and ign timing at 10 deg BTDC   recently switched from the 45 dist with points to my 25D with pertonix *~*~*

115/115 MOP is NOT appropriate for the 104 cams.   Compared to where the cam was designed to run, 115 retards the intake 11°, advances the exhaust 11°, and reduces the overlap 22°.   You're applying emissions MOP timing to a performance cam...  apples and pomegranate.

At the very least, re-set the existing pulleys to 110/110 MOP, which is 'less wrong'.   But to do it right, purchase a set of 104 MOP pulleys and time the 104 cams properly.   You have the higher compression to support the cams,  now time them properly.

Mechanically,  the 43/45 series distributors are superior to the 23/25 series... it was just design evolution, and newer was better.   But this many years down the road,  it may well be a matter of which one is still in better 'used' condition.

Either series distributor will benefit from an electronics "points replacer" ignition system.   If you were starting from scratch and both distributors were in good condition,  I'd suggest going with the 45 and Pertronix (not that I'm pushing Pertronix...  but you mentioned it).   But your 25D is installed,  so if it's in good condition,  then there's no reason to replace it.

If either distributor needs work,  then send it to Jeff Schlemmer at Advance Distributors.   He can rebuild it to better than new condition,  re-curve the advance to anything you want,  and install an electronic ignition.   Good work, reasonable prices.

Jeff Schlemmer,
Advanced Distributors
1149 Quincy Street
Shakopee, MN 55379
(612)-804-5543
    jeff@advanceddistributors.com  e-mail, from website
    http://www.advanceddistributors.com/  website

Last edited on 08-30-2017 03:59 pm by Esprit2

subwoofer
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Esprit2:

You obviously know these engines well, do you have any experience with upping the compression for the 2.0? SJ Sportscars can provide 11:1 pistons for the 2.0, which (I guess) would be good in concert with a pair of 104 cams.

--
Joachim

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John,

There really is very little emperical data (dyno runs) to differentiate the various combinations of cams, sprockets, carbs and ignition settings.  However, thanks to people like Tim the JHPS board contains a lot of information to help people piece together some ideas.  Others have been kind enough to share their data so we can examine the dubious 'should' and 'ought to' statments that are out there.

The data out there suggests the dual 104 cam combo on 104MOP sprockets produces extremely 'peaky' results (http://www.lotusbits.com) with not much usable power in the everyday driving range.  One could argue shifting to 115/115 timing would produce more low-end torque and drivability.   Get a set of 104MOP sprockets, then find us a dyno shop and let us know!

Instead of dropping $1500.00 on a set of Dellortos, how about putting a 107cam on that exhaust and using those 104MOP 'green dot' sprockets.  My personal experience with various combinations suggests it is hard to beat the Excel SE 104/107 set-up for power and drivability.

Judson

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I'm outta the JH game for a bit and only poke my head in here occasionally these days - but it's good to see ya back Tim!  I also subscribe to S1S2s3 forum. 

Cheers,

Esprit2
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Judson Manning wrote: (Snip)... The data out there suggests the dual 104 cam combo on 104MOP sprockets produces extremely 'peaky' results (http://www.lotusbits.com) with not much usable power in the everyday driving range.  One could argue shifting to 115/115 timing would produce more low-end torque and drivability.   Get a set of 104MOP sprockets, then find us a dyno shop and let us know!
Judson,

It's a big leap from minimal available data to a firm statement that 104 cams on 104 MOPs produce extremely 'peaky' results.   It's true, the power curve isn't as broad, or as strong below 3500 rpm as it is with a pair of 107 cams,  but a pair of 104's is not "extremely peaky".   They start to take off around 3500 rpm,  pull like a train from 4000 rpm on up,  and eagerly blow right past redline if you let them.   I know,  I do have a pair of 104's/ pair of DHLA45's/ 37 chokes on an otherwise stock Federal 907.   It doesn't even have the advantage of a desireable higher compression ratio.   It's not a trial to drive on the street,  but it does offer much improved top-end.

It's not 'cammy',  it idles smoothly,  and if you lug it down it will pull away smoothly under throttle without complaint.   Granted, you need to shift down if you want it to pull away smartly from "down low",  but it's not like driving a cammy "full race" hotrod small block that won't idle.

I know from experience.   I installed the 104's in 1995 and used the car to commute to work in congested metro traffic and it was never a problem.

I don't suggest 2 x 104's on 104 MOP's for anyone in search of a mild mannered gentleman's cruiser... use the 107's.   But it does bother me when folk who haven't lived with the 104's talk in all or nothing terms about how bad they are.   They aren't bad in traffic,  and what they offer to the more spirited driver on the open road can't be touched by 107's.   What does the owner want?

I also have a pair of DS2 cams on a 2.2 converted 907 hotrod.   They're hotter than the 104's,  but still trundle through traffic without complaint.

Last edited on 05-26-2009 08:57 pm by Esprit2

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subwoofer wrote: (Snip)... do you have any experience with upping the compression for the 2.0? SJ Sportscars can provide 11:1 pistons for the 2.0, which (I guess) would be good in concert with a pair of 104 cams.

--
Joachim


Joachim,

The 907's semi-hemi combustion chamber is very tolerant of higher compression on pump gas.   11:1 isn't a problem on the pump gas available in the USA.   Of course, a lot will depend upon the gas where you are.

If you're considering 104 cams or hotter,  then raise the compression to at least 10:1.   11:1 would be good if you wish to drive in a spriited manner,  but a waste of high octane fuel if you'll be trundling along in traffic most of the time.   Be sure you know what you want,  because it's not a simple change later.

I have a pair of 104 cams in a low compression 907,  and it works well.   I just know that it could work much better with higher compression...  the cam's true potential isn't realized when matched with the low compression.

If you're thinking 104 cams and Hi compression,  then also consider a pair of Dellorto DHLA45E's with 36 or 37mm chokes.   The 37's are more in keeping with the 104s and hi-compression fun mentallity.   But if you think the majority of your driving will be trundling around town,  then go with 36mm chokes.   They give up some top end, but the engine will be more commute-friendly.

Last edited on 12-10-2016 07:22 pm by Esprit2

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Joel wrote: (Snip)... it's good to see ya back Tim!  I also subscribe to S1S2s3 forum. 


Thanks Joel,

I just bopped in over the quiet holiday weekend and saw an interesting thread.   I'll fade away again as this thread fades... see ya over on the Lotus list.

Last edited on 05-26-2009 09:13 pm by Esprit2

subwoofer
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Esprit2 wrote:
The 907's combustion chamber is very tolerant of higher compression on pump gas.   11:1 isn't a problem on the pump gas available in the USA.   Of course, a lot will depend upon the gas where you are.

If you're considering 104 cams or hotter,  then raise the compression to at least 10:1.   11:1 would be good if you wish to drive in a spriited manner,  but a waste of high octane fuel if you'll be trundling along in traffic most of the time.   Be sure you know what you want,  because it's not a simple change later.


The cars will not be used for commuting, so that is not much of an issue. From what I can remember from the thermodynamics course I took way back when at university, the thermal efficiency will go up quite a bit with higher compression, so for cruising at highway speed, the upped compression should be good.

Regarding the pistons: to date I have only seen higher than 9.5:1 pistons for the 2.0 from one single source, and I can't help but think there must be a reason why, since 10.9:1 and 11:1 pistons are abundant for the 2.2. According to the source, they are actually lighter than the stock pistons, so weight should not be an issue.

As far as carbs go, I am about to order a set of 45mm Dell'Ortos.

--
Joachim

Last edited on 05-26-2009 09:08 pm by subwoofer

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Joachim,

If you have the option,  order the E version of the Dellortos... 40E or 45E.   The differences are in small details like fine pitch threads on the idle mixture screws.   The overall performance is unchanged,  but it's easier to fine tune the carbs.

Also, look for Lotus spec carbs.   Lotus worked very closely with Dellorto and many details in the carbs used on their engines were specifically tweaked for them.   The idle progression 6-hole pattern was specifically developed for the 9XX and makes a worthwhile difference.   Many of the details Lotus developed later became standard features across the Dellorto line,  but the Lotus progression holes remain Lotus-specific and never became Dellorto-generic.

The higher compression, all by itself, is good;  however, hi-compression also forces the need to burn more expensive hi-octane fuel.   So, from a cost efficiency basis,  is it still better?   If the goal is economy,  then HC may not be worth it.   If the goal is performance,  then yes, by all means go with hi-compression.   11:1 is a good street ratio.

JE Pistons offers high quality forged aluminum pistons for the 907 in just about any CR you could want.   I've not done a survey and don't know what other brands are readily available.   There isn't a structural reason why more pistons aren't available for the 907.   It's just demand.   It costs to develop any product,  and there just aren't enough 907's on the road to get every manufacturer excited about jumping into the market.

Consider installing the stroker 2.2 crank.   It's the best thing you can do for a 907.   Regardless of which crank you use,  use a cross-drilled version with the bearing shells that go with it.   If you stay with your existing 2.0 crank,  you can have it cross-drilled.   Then use the later bearing shell for the X-drilled crank configuration.

Last edited on 05-26-2009 09:36 pm by Esprit2

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Tim,

We've had the opportunity to disagree in the past.  I do have the data with which to base my claims, and to date you haven't produced any.  While I do appreciate your personal experiences, they are after all subjective and wildly open to interpretation.  

To make the emphatic statement "The 104 cams require 104MOP pulleys (sprockets)" is about as ridiculous as your narcissistic "I know from experiece" comment.  The only way to answer John's question is to put the car on a dyno and adjust the timing until it produces the results he wants. 

When you can measure what you are speaking about and express it in numbers, you know something about it.   Your daily commuting ritual and your seat of the pants evaluations don't give us a single thing we can use. 

Just like the carb jetting disagreement years ago, when you have some actual data to counter my statements, feel free to criticize me all day long and defend the 104 to your heart's content.  

 Judson

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Judson Manning wrote: Tim,

We've had the opportunity to disagree in the past.


Judson,

Well, see there, we don't disagree about everything.

Judson Manning wrote:
Just like the carb jetting disagreement years ago, when you have some actual data to counter my statements, feel free to criticize me all day long and defend the 104 to your heart's content.


You were trying to apply Spec 9 DHLA45E jetting to 45D PowerJet carbs without recognizing the fundamental differences between the two types of designs.   And then you complained the result was rich and Spec 9 was no good (I believe you likened the result to fogging mosquitos).   Of course it was rich,  you were double fueling.   First line in any of the Lotus carb specs is the carb body to which the jetting is to be applied... ya can't ignore that.

The reason I defend 104's is because you blast them.   They're good cams for someone who is looking for a little performance;  but no, they're not right for someone wanting a relaxed cruiser.   Mild cams and timing are not the only solution for a 907.   Different horses for different courses... open your mind.

I left this forum a couple of years ago primarily because of the intolerant, territorial, myopic views of two people.   You were one of them.

After a long absence, I pop in for a visit and you're right there ready to be intolerant again.   I expected it, but was hopeful anyway.   Unfortunately, you quickly confirmed my worst expectations.

I'm outa here.   Anyone who wants an opinion other than Judson's knows where to find me.   See ya elsewhere.

Last edited on 05-29-2009 06:26 pm by Esprit2

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All -

John hinted at the beginnings of this little adolescent side-show "...i know this gets discussed...but I never saw an answer"

Like all good Americans, I will defend to my dying breath Tim's right to express his opinion.  However, answers and opinions are not synonymous, and you can't derive an answer from a philosophical discussion or revisionist history - only through experimentation and careful analysis of the resulting data.

For the record:  I didn't blast the 104 cam and I really don't think the 104 needs a White Knight to protect it, but that's just my opinion.  Contrary to his post, I do have experience with the 104, and no I wasn't trying to apply Spec 9 jettings to PowerJet carbs either. 

Getting back to the question:  To everyone out there with the means, please take your car to a local dyno shop, or organize a local dyno day with your local club and help us collect data.  The more data we have the better idea we have on answering these questions and putting an end to these adolescent distractions.

Judson

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Dynos are the best way. We just took and MGA up to the dyno shop and merely playing with jetting and timing realized a 23% increase in rear wheel horse power.

Happily this week we are going up to pick up a new engine dyno. That will really help out at the shop.

I guess now I'm going to have to build a new motor just to see what can be done. =)

Mitch #19670

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Esprit

Thanks for the detailed response. 

Sorry for the late reply i thought the site would keep sending emails with each response so imagine my surprise when I logged in and saw the thread.

I guess now I need to verify the cam grind West Coast Cylinder heads did for me and the compression on the pistons from Delta. 

I can add this  timed balanced and mixture set right the engine has lots of speed in the 4000 to 7000 rpm  range,  and idles in traffic at 1100 rpm even with the pulleys at 115 /115   I'll try 110 /110  soon

thanks  Esprit and Judson.   play nice and share your toys

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I have a 1974 Jensen Healey with stock engine except Strombergs were replaced with a single Weber DGEV32/36 and electronic ignition. I recently purchased the car and trying to get it running smooth, idles rough but runs ok at over 2000 rpm's (or at least seems to). I have been reading quite a bit about timing and cams. My car has 110 mop intake and 115 mop exhaust (at least that's what is on the cam pulleys). Timing at idle (950 to 1000 rpm) is approx. 12 deg btdc.

What affect does this cam combination produce?

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Hi,

I have been reading a lot of the topics concerning the cam timing, and there is a lot of valueble information on weather to go on 110/110 , 115/115 MOP
Also on cam types c,107,107 and cam sprockets.

I am a little confused about the meaning of these figures.
Normally I would set the ( messure) the cam timing in deg btdc and atdc for both open and closing.

Is there anyone who can explain the MOP figures and the cam sprockets numbers and how they compare to the opening and closing angle of the valves .

Cheers
Kim

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MOP is also known as LCA, Lobe Centre Angle.

For 260 degree cams and 110/110 timing, you will have the following timing:

Ex: Open 60 degrees BBDC, close 20 degrees ATDC
In: Open 20 degrees BTDC, close 60 degrees ABDC
Overlap: 40 degrees

Same cams, 115/115 timing:
Ex: Open 65 degrees BBDC, close 15 degrees ATDC
In: Open 15 degrees BTDC, close 65 degrees ABDC
Overlap: 30 degrees

I am no expert, but large lobe separation angles are by some (like David Vizard) claimed to be a band-aid to make too-long-duration-for-the-purpose cams behave on the street. His claim is that the ideal lobe separation angle is an engine characteristic and that cam duration should be chosen for the desired overlap at this particular LSA (or (MOPex + MOPin)/2).

Since later 907s and 912s came with 104 degrees LSA, this could be considered to be a good choice. Vizard claims that too narrow LSA is preferable to too wide LSA, and that the ideal value varies in the interval 110 to 100 degrees depending on valve geometry and head flow.

So for streetability, that theory would indicate that you need short, high-lift cams at 104MOP. The 107 cams did just that, shortened duration and higher lift compared to C, D and E cams.
--
Joachim

Last edited on 01-31-2014 09:17 am by subwoofer

roland11a
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Very usefull thread as i'm just at this point in my engine re-build.

Can somone shed some light on the cam belt sprocked retaining bolt and washer? The main list of torque setting in the workshop manual state 25 lbft however further on, in the actual section 56 lbft. is one initial and one final?
Also at this torque the thick retaining washer just bends/dishes where the centre hole of the sprocket stands proud from the end if the camshaft by about 1/8"
should there be a spacer behind?

Thanks

Barthol
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Hi Again,

I think that I am getting closer to be a little wiser:-)
Looking through the answer from "Subwoofer" I conclude the following:

Inlet cam: MOP ( Max opening point) of 110 means that the maxvopening point occurs 110 deg. after TDC

Exh.Cam: MOP of 110 means that the max opening point occurs 110 deg before TDC.

Is this correctly understood?

Then some more questions.

Looking on my cam wheels they are reversible and marked ink and exh on both sids, on one side there is also a raised dot in the casting.

Can anyone clarify wether this is 104 or 107 mapping?

My cams are definitely C-cams with the low lift,
I am building a 2,2 ltr engine with 45 mm dellortoes, and app 9,5:1 in CR.

Can I with susses use these cams / cam wheels. or do I need to go for other options.( the car must be torquey and is only used in traffic,- no racing)

Last question. When I measure the opening and closing angles of the valve, what clearance do I need between the Cam and the followers. Normal setting with cold engine or "0" clearance with cold engine??

I know it is a lot of questions , but any help will be highly appreciated as , I want to get the engine as r"Right" as possible the first time.

Thanks lot.
Kim

Art DeKneef
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Let me say I am as confused as you are and am trying to figure this out on one of my cars now.

It sounds like your engine is from a 1974 car.

I'll answer what I can. The C cam is the stock cam that was standard in all JHs. There is no 104 or 107 mapping with the C cam. The 104 and 107 refer to different grinds that Lotus used in different variations of the 907, 910 and 912.

The pulleys are reversible. One side goes on the intake cam and the other side goes on the exhaust cam. Then you line up the marks accordingly. This gives you your cam timing.

You are building a 2.2 L engine with Dell 45s and higher compression. Based on what I have read and understand, you will need to use either the 104 cams, 107 cams or the 104/107 combo to get the power I think you want out of the engine. Using the stock C cams will limit the engine. But with the 2.2 crank it may be torque enough for you. I don't recall anyone doing a stock 2.0 engine to a 2.2 that didn't change cams also. If there is hopefully they will chime in and share their experience.

According to the shop manual there are 2 types of cam pulleys. The original (side 1: 110EX, 115IN - side 2: 115EX,110IN) type covers the years 1973 and 1974 up to engine 10480. After engine 10480 there is a new pulley (side 1: 110EX, 100IN - side 2: 115EX,110IN) that went on catalyst equipped cars.

If I understand you correctly on the clearance between the cams and followers, the shop manual recommends valve clearance cold of 0.005-0.007in inlet and 0.010-0.012in exhaust.

Barthol
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Hi,

Just did some more measuring
I measure the lift of the cams to be 9 mm app 0,359".
The camshafts have no stampings but they have 2 groves in the front indicating E-cams?? ( I believe that the lift of the E cam should be around .340"??

looking on my cam wheels they are reversible with the txt EX and IN in raised text on both sides of the cam wheel. Additionally there is a raised dot on one side of the Cam wheel.
Measuring clockwise from thee keyway to the in -marking I measure 162 deg and the same measurement to the ex mark is 198 deg.

anyone who can clarify what exactly I have , and wether it would be the right choice for my project.

The question I had about the valve clearance was only at which clearance I should use when determening the opening and closing degrees .

have a nice weekend
kim

Jensen Healey
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The E cam has 2 grooves but the lift should be 0.344".

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&ved=0CIUBEBYwCw&url=http%3A%2F%2Fusers.ox.ac.uk%2F~ohare%2FCam_Data.xls&ei=dyE_U5i9E-TAyAHpn4GoBw&usg=AFQjCNFoIxrFTBT3oEmFzNTI9hzg81M5_A&sig2=pf99R9nUtgm6iRIeKgSjrQ&bvm=bv.64125504,d.aWc

This is an Excel spreadsheet with tons of info.

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Back in the mid 90's I put a 2.2L crank and pistons in my JH5. I did not change anything else, even the cam timing was still 115/115. The off-the-line torque was much better, but I do not remember it being that much better otherwise. But then, I was not racing it, just having fun commuting to work and such.

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Hi Barthol,

 

I will be very interested in hearing how your car goes with the 2.2 conversation.

 

I too am building a 2.2 with 9.5:1 comp ratio, 45 Delorto's, and have a later lotus head with the ‘E’ spec cams. I have spent the money and everything has been dynamically balanced and due to be put back together after being off the road for more years than I care to mention.

 

I bought my 2.2 crank from Gary Kemp and speaking to him he said for a road going engine I will be more than happy with it. The guys from Lotusbits in the UK said the ‘E’ spec cams were never fitted to a 2.2 engine and as a minimum I should buy a set of 107's but I am going with Garry’s recommendation as I am looking for drivability and reliability more than anything else.

 

Please let us know how it runs, good luck.

Cheers Carl

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hi Just tested my timing and it lucks like my cams are app 252 deg with valve clearance of 0.2 mm.
Inlet opens 14 deg BTDC and closes 58 deg ABDC which indicates o me that the pulleys must be 110 MOP?

do anyone know at what clearance the opening and closing degrees normally is measured at?
I recon that an increase in clearance will give a later opening and an earlier closing and thus a shorter opening duration all together.

I knbow when i worked with old Triumph Motorcycles the opening and closing figures in degrees was always given with 0 clearance..

To carl. I think i will try to get a 104 /107 combo with 104 MOP pullies.

Cheers
Kim

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Hi lads,
If you are going to purchase cams, I would highly recommend checking with Richard Reyman at West Coast Cylinder Heads: http://www.proheads.com/

Richard built up the 907 engine in YELODOG and does his own cam grinding.  He did a fantastic job on my engine (240 hp) and may have some 907 cams laying around - or he can grind a set to match the other changes in your engine.

He is well versed in the 907 and had several JH that he used to race.

Pete Bahr

Barthol
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hi anyone who knows the normal opening and closing figures are given??
br
Kim

Barthol
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sorry
I meant at which valve clearance is the normal opening and closing figures of the valves given?
Best regards
Kim

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I'm sorry I never really understood cam timing. Since the cams and pulleys are fixed, there is no adjustment to be made unless one purchases adjustable pulleys. Even then, they would be set to 104 for the 104/107 cams.

Kurt

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Hi Kurt,

That makes sense:-).

My problem is that I have two set of Pulleys, and I want to find out which they are.
Trying to measure with a dial gauge I get max lift at 106 deg???

I measure the lift of the valve and the angle of the crankshaft close to max lift.
Then I turn the crankshaft until i get the identical lift ( after the max lift of the valve), and read the angle on the degree disk on the Crankshaft. The MOP should then be directly in the middle of the 2 readings.

But 106 ?? it is closer to 104 than 110. but is this way of measuring the MOP accurate enough.
There is no longer colored dots on any of the pulleys

Anyone now of a safe way to identify the Pulleys?

Cheers
Kim

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I have a 75? (build date Dec.12/74) five speed which I have recently replaced the timing belt and tensioner, the tensioner quit after 41 years. When I set the engine up to 110degress on both cams there is no compression at 115 on both it 125lbs per cylinder, but spits back through the carbs. The timing is at6 degrees before TDC If is retarded more it idles at 2 grand. Help

subwoofer
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You say the tensioner "quit" on you, did the belt jump or break on you? There is not much to go on before pistons and valves meet, at two teeth off it's very close.
It sounds to me like your cam and spark timing isn't even close to the ballpark, retarding the timing will NOT increase RPM unless you are over advanced to begin with.

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Nothing came in contact as far as valves and pistons, I've been down that road, the bearing in the tensioner broke up and the engine died as quickly as it fired. There is good compression in all cylinders and the engine fire instantly now that it is put back together but it is not right. This is my fourth go round with one of these cars and about to be my last if I cant get past this issue

subwoofer
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The Strombergs are IMNSHO a piece of s}#% and could well be the reason for the 2k idle. Check the butterfly axles for radial play, if you feel any then toss them.

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I'd love to but cant afford the replacement Dellortos

Randallclary@icloud.com
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I changed to Dellorto and have a great set of Strombergs. If you want them, make me an offer. I'm sure you would be happy. I rebuilt them prior to the stroker crank decision. Where are you located? I'm in Riverside, CA

subwoofer
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I'm trying to figure out what you meant by the "no compression at 115" bit. There are a few possible culprits here:

Errors in cam timing

Errors in spark timing

Vacuum leaks

If you have the stock federal setup there are plenty of possible places for a leak to occur.

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No compression occurs at 110 timing the car runs at115

westsideclay
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What do you need for them I'm in Huntington Beach. The car us in Winchester at my brother's house

subwoofer
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Your cams must be WAY off!!! 5 degrees difference in cam timing does not change from no compression to normal compression readings.

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The cams line up with the correct firing order, everything is where it is supposed to be which is why I cant figure this out

Brett Gibson JH5 20497
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my 2 cents.
Double check every thing, set the crank at TDC pull the #1 plug and make sure the piston is at the top as well. next check to make sure the cams are aligned, 110 or 115 won't make any difference on compression. Next the distributor, make sure the rotor is pointing to the #1 position on the cap and the wire actually is going to the #1 plug, also make sure the distributor is firmly seated in the housing. Do this before you even think of touching the carbs, the strombergs are the last thing you want to mess with right now, they are a good dependable carb and easy to work with, but not as refined as Dell's. Stick to the basic's

Brett

subwoofer
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And you have the IN mark facing you on the intake and EX on the exhaust? The sprockets flip over depending on which side of the head.

subwoofer
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Please post a picture of the sprockets from the front with crank at TDC.

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Yes and the marks line up, there are no dots on the cam wheels as the have probably been cleaned repeatedly and been erased over time, but there are timing marks in the cam wheel which are aligned and correspond with the firing order. There has been no contact betweenthe valves and pistons

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There are one or more notches on the rim, and there should be a marking stamped in. Changing from one timing to the other includes flipping the sprocket over.

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I didn't have to flip the sprocket over to change the timing the marks are as your picture shows on both sprockets

subwoofer
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Please note that one mark is "in", the other is "ex". You HAVE to flip they, otherwise they are three teeth off!

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They are lined up intake to exhaust 115 to 115

westsideclay
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This is the part that is baffling because I have done this several time before and never had anything like this happen

subwoofer
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Please get yourself a basic understanding of what you are doing before going any further. Moving the cams three teeth does not constitute a 5 crankshaft degree change in timing, it is more like 60 degrees. You are lucky if valves and pistons haven't kissed.

Before going any further you have to make 100% certain that the cam timing is correct, and that includes having the IN and EX marks visible on the correct sprockets for the actual marks you are about to line up.

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I have done all this the car will run but not well. When the cam covers are removed and the engine is at #1TDC. the cam shafts align correctly to correspond the firing order. When the engine is rotated through by hand everything goes through the cycle as it is supposed to . There hasn't been any contact between the valves and the pistons

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I really appreciate your help on this

westsideclay
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Thanks Brett I've done all of the above and have not achieved the result I expected

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But you still haven't answered the fundamental question, are you using the correct marks? Don't ASSUME anything, VERIFY.

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Yes those are the only marks on the camwheels and the camshafts are positioned correctly

subwoofer
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You can't tell if cam timing is off by looking at the cams, the changes required to make it run like a bucket of excrement are far too small.

You would probably want to run 110/110 timing instead of 115/115, but that would require the correct markings. You could of course make those marks yourself if you only have 115 marks. I could send you the other side of the sprockets as well.

Once properly timed, ignition is next. Set according to instructions, I think vacuum lines should be disconnected for this, while at it check the vacuum capsule for leaks.

Vacuum leaks easily give a 2k idle, I know from experience.

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That was my original suspicion because I had a high idle when my brake booster was shot . The spitting back through the carbs is what bothers me the most

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I don't know for sure, but I suspect that the closer timing would spit less. Some you have to live with, that is why we have air filters...

The best MOP for these engines is 104, 110in 97ex is basically that, just 6 degrees advanced. Advancing the cam is common on other designs, but they usually only advance 2-4 degrees.

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Thanks I really appreciate your help > I think it's time for this one to finds a new home as I really don't have anywhere suitable to work on it close to where I live and don't have the time to commute to where it currently is

subwoofer
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It shouldn't take many hours to get it running fairly well, if the rest of the car is in good nick it would be a good learning experience.

westsideclay
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the rest of the car is in good shape. The body is straight with very little rust I just put shocks tires and clutch into it. It needs an interior as its worn out and Healey dashpads did not play well with the Southern California sun I am in the process of deciding to keep the car or move on to something different. I truly appreciate your input on this but I'm really not looking forward to another learning experience. It would be different if ther was a good independent shop locally but unfortunately most have closed their doors

Esprit2
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I'm late to this thread, sorry if I'm beating a dead horse.

Westsideclay, Subwoofer and Brett have given you good advice on how to time the cams, you repeatedly insist that is what you have done, but it's not.

> The cams line up with the correct firing order,
> everything is where it is supposed to be which
> is why I cant figure this out

No, it's not where it's supposed to be, which is why it doesn't have compression, and doesn't run. You're setting the cams incorrectly. Please clear your mind of what you have done, and please read through the following with an open mind.

You CAN NOT change the cam timing from 115-115 to 110-110 without first removing both pulleys from the engine, flipping them over front to back, and re-installing them. If you have not removed/ flipped/ replaced the pulleys, then you have not re-timed the cams correctly. Simply rotating the pulley 3-teeth without first flipping them changes the cam timing by 54 degrees, not the 5 degrees you seek. If the pistons have not hit the valves yet, then you are extremely lucky. Head for Vegas while you're hot.

Set the cams back to 115-115 where it runs.

Grab a felt tip pen.

1) For each timing mark on the pulley's rim, follow that tooth to it's opposite side, and there you will find another mark of the same number value. Or you should!! If there's no timing mark there, then put one there. At least temporarily with a felt tip pen.

On the INtake pulley, the front-facing 115 timing mark should have a little 'IN' stamped adjacent to it. On the back side of the pulley, the second 115 timing mark will have an 'EX' stamped by it. At least that's the way it should be. If the second 115 mark isn't there on the back side, use the felt-tip pen to put it there. And if the IN and EX marks are not present, write them in as stated above.

Similarly, on the EXhaust pulley, there should be '115' and 'EX' engraved near the timing mark on the front face of the pulley rim, plus '115' and 'IN" on the back side.

With the crankshaft set to TDC, make certain the pulley's timing marks aligned on the imaginary centerline between the cams. Simply aligning the dots with one another is not enough, they must also be on the imaginary centerline. If they're aligned but not on the centerline, then the cams are not properly timed.

2) On the INtake pulley, start on the pulley TOOTH that has the timing mark on it, and count downward (clockwise) three teeth. Counting the tooth with the 115 timing mark on it as '0' (zero), count down 1, 2, 3 teeth. Use the felt tip pen to color that 3rd tooth black.

3) Similarly, on the EXhaust pulley, start at the timing mark, count downward (counter-clockwise) three teeth, and color the tooth black.

4) For both teeth in steps 2 & 3 above, write '110' near that newly identified tooth.

5) On the INtake pulley, also write 'IN' next to the new 110 tooth.

6) On the EXhaust pulley, write 'EX' next to the new 110 tooth.

7) On the INtake pulley, start on the 110 tooth on the front side, follow that tooth to the back side (rearward facing side), and write '110' and 'EX' near the back side of that tooth.

8) Similarly, on the EXhaust pulley, follow the new 110 tooth to it's back side, and write '110' and 'IN' near the back side of that tooth.

Now, the 110 marks on the BACK sides of the two pulleys are what you want to have on the front side.

9) Remove the INtake pulley, flip it over front to back, and re-install it. 110 IN is now facing forward.

10) Remove the EXhaust pulley, flip it over front to back, and re-install it. 110 EX is now facing forward.

11) Rotate the pulleys three teeth to align those new 110 teeth on the imaginary centerline between the camshafts.

12) Re-install the timing belt and tension it properly.

Now both cams are timed to 110 MOP.

Make certain the timing belt's orientation on the auxiliary pulley doesn't change (ie, the same teeth engage after the timing belt is replaced. Any change of tooth mesh at the auxiliary pulley will require a corresponding change to the distributor's timing, so it's less work to make certain the aux pulley's registration on the timing belt doesn't change.

If nothing else has changed, then expect the idle rpm to be slightly higher with the new cam timing. Let the engine fully warm up, then re-set the idle speed to 900 - 1000 rpm.

Good luck,
Tim Engel

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Thanks for your input but as I stated previously I'm on hiatus while I decide if I want another "learning experience" with this car I shouldn't be having this problem as I built the engine in the first place and drove the car for eight years before this. When I decide what I'm going to do I'll get back into this.

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Hi All,  I'm a new JH owner and learning the ropes, i request your patience.

I'm trying to work out this timing, it was done by my late father. I know my way around an engine but not specifically cam timing, it's a little over my head for the time being.

Would anyone know what the MOP timing of the white marks are? I understand MOP yet it's the why i don't understand. I remember when we first drove it home it was terrible but after a few months it was running very very good!

I'm yet to turn over the enigine, even by hand as it's been sitting for a while so i have some work to do.

Not sure yet how to post two images in sequence yet, i will post another below of his thoughts at the time which may help.

Attachment: WhiteMarks.jpg (Downloaded 88 times)

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Camshaft Drawing

Attachment: Camshaft1.jpg (Downloaded 89 times)

Esprit2
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The second file, the camshaft drawing, is pretty illegible. I've reversed the color bias so that it has a white background, but the resolution is still low, fuzzy. Can you re-write the notes in a message here?

What cams are installed in the engine? Can you confirm what MOP pulleys are used. From what I can see, I presume they're the standard Lotus dual MOP pulleys, 110 red dot and 100 blue dot. But it's not good to guess when timing cams, so please confirm the starting point... what cams and pulleys are installed?

For the sake of conversation, let's say the pulleys are the 110 MOP (red)/ 100 MOP (blue). In that case, the first thing for you to understand is that there were separate single-MOP pulleys that were true 110 MOP (red) and 100 MOP (blue). But 110 and 100 do not fit on the same pulley, so the 110/100 dual MOP pulley cheats, and the blue dots are really 97 MOP, not 100. If your father had tried to reverse engineer the pulley's math based on 110 and 100 being 4 teeth apart and the pulley flipped over, it would have driven him nutz... it doesn't work.

Also, there are 40 teeth on the pulley, and 360 degrees in a circle, so 9 degrees per tooth. However, cams are timed in 'crankshaft degrees', and there's a 2:1 ratio in crank & cam speeds. Therefore, each tooth is 18 crankshaft degrees. One tooth beyond the red dot 110 MOP advances the cam timing 18 degrees, or 92 MOP, which is not a useful value with the OEM cams.

The white marks in your first photo have no value in timing the stock J-H 907 cams.

If the cams are stock C-cams, and the pulleys are 110/100 (97), then the best cam timing to use is 110 IN and 110 EX. The Lotus 100 (97) and JH 115 MOPs were emissions settings, and results in a loss of power compared to 110 IN/110 EX.

The photo shows the pulleys to be installed the correct way around. The raised bump on one spoke faces forward on the exhaust pulley, and backward on the intake pulley. That's correct.

Now, rotate the crank until it's at TDC. Then the red dot next the the IN mark on the intake pulley should align with the red dot next to the EX mark on the exhaust pulley. That will give the design-correct 110/110 MOP.

The original JH 115/115 MOP reduces power output about 10 Hp. If you want to use that setting (why ??) it's also on the 110/100 (97) pulley, just not marked.

In your first attachment, the photo of the pulleys, refer to the intake pulley... it's the most straight-on shot, and the easiest to read.

The timing dot farthest to the left/ counter-clockwise (nearest the white mark) is red, or 110 MOP. The alternative blue timing dot is 4 teeth clockwise, and is 100 (97) MOP... EXCEPT it's next to an EX mark. Follow that tooth to the back side of the pulley, and you'll find a second blue dot next to an IN mark. To time the cam to 100 (97) MOP, the pulley must first be removed, flipped over front-to-back, and re-installed (ie, raised bump facing forward on the intake pulley, or facing backward on the exhaust pulley). Then rotate the INtake pulley until the blue dot next to the alternate IN mark aligns with the dot next to the EX mark on the EXhaust pulley.

Similarly, the missing 115 MOP dot would be three teeth to the right/ clockwise from the red dot, on the tooth next to the tooth with the blue dot... next to the EX mark. Again, follow that tooth to the back side, and that's where the 115 dot would be next, to the IN mark.

So you have your choice of three MOPs with the pulleys shown in the photo. But, IMHO, unless local emissions inspections will not allow the OEM cam timing to be altered, there's no desireable reason to use either of the alternative MOPs, 100 (97), or 115. The engine will run it's best if you time the stock cams to 110 red IN / 110 red EX.

But before taking all that to the bank, first confirm what cams are installed in the engine, and look for any marks stamped on the pulleys that indicate the MOP. Normally, the MOP would be stamped on at least one side.

Good luck,
Tim Engel

Attachment: JH Cam Timing for qwerty - White Background.JPG (Downloaded 65 times)

Last edited on 10-10-2016 06:52 pm by Esprit2

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JHPS allows file attachments up to 102kb, and your drawing is only 17kb. Do you have a higher resolution version that you could post?

Regards,
Tim Engel

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Thanks Tim, that sheds a bit of light on the subject.

I'm sure he knew that the 110/110 timing was correct for the engine without emissions and is why the white marks have piqued my interest, maybe he messed about with the overlaps as seen n the drawing allowing it to breathe a little better. It has DHLA45's on it. I doubt is has a different Cam but i will check ...how do i check?

I'm sorry i can't get it any bigger that the attachment without going over the limit.

The Notes to the bottom left are:

RED DOT        110 MOP
BLUE DOT       100 MOP
YELLOW DOT  102.5 MOP
GREEN DOT    104 MOP

EUROPEAN SPECS  INLET 102.5 A.T.D.C.
                              EX   102.5 B.T.D.C.
NORTH AM SPECS  INLET 100    A.T.D.C.
                              EX   110    B.T.D.C.

Attachment: CAM.PNG (Downloaded 63 times)

Last edited on 10-10-2016 08:39 am by qwerty

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Absolutely no numbers on Cam wheels, front or back.

Attachment: IN.JPG (Downloaded 62 times)

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Ex

Attachment: EX.JPG (Downloaded 62 times)

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"If the cams are stock, and the pulleys are 110/100 (97), then the best cam timing to use is 110 IN and 100 EX. 100 (97) and 115 were emissions settings, and results in a loss of power compared to 110 IN/110 EX."

Is that a typo Tim, should that read 110 IN /110 EX?

I apreciate your knowledge Tim, i've read quite a few of your posts regarding cams in order to understand them.

Regards
Peter

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You have both cams installed with Red Dot (110MOP) as the valid timing mark, but if I am not much mistaken they have been timed one tooth advanced (if the white marks are anything to go by).

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That's what it looks like yet for anyone reading please note  i am a complete novice when it comes to Cam Timing.

I wan't to get it running with this timing first. I remember spending a lot of time on this and at the end of it all the JH ran very very well. Dad without doubt knew what he was doing, i know that much. Timing it to Red dots 110/110 would have been a no brainer for him as i have already learn't through reading and he would have done through calling people in the know. He didn't have access to internet resources back then, only a bunch of manuals sent over from Cropperby Bridge and AutoCad. This is the whole reason i'm exploring this. Maybe it does have non standard cams, as yet i do not know. Maybe it's to let the DHLA 45's breathe.

For now though i have to get over the damned Manflu. Greg's box of goodies (ps thanks for packing the inside rad hoses with styrofoam haha, i'm assuming this is so they wouldn't be crushed in transit??), a Gates blue belt, wheels, tyres, tools and steering wheel came in last week and i was all set to have a dirty weekend untill the sniffles happened!!

Last edited on 10-10-2016 10:43 am by qwerty

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Tim,

Thinking out loud here, Could this be the end result of the Aux pulley being out by 1 or more teeth and correcting for it?

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That would make things even worse, as the ignition timing likely would be out as well (although that can be corrected by turning the dizzy).

But I know for a fact that a 907 with C cams (standard issue JH spec) will run two teeth off on the cams, just not well. Open the cam covers to look for the cam markings, IIRC the standard JH cam will have a number of 'C's stamped in somewhere behind the pulley seal, later Lotus spec cams will have an 'E' (Eclat/Esprit S1), '4' (104-cam, intake side on later NA engines) or '7' (107-cam, turbo spec).

Any aftermarket cam would not be ground one tooth off for sure.

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Joachim

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Thanks Joachim,

I will be taking the cam covers off later this week or on the weekend. I will look for markings.

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qwerty wrote:
(Snip)... I doubt is has a different Cam but i will check ...how do i check?
On the stock, OEM cams, there were marks on the bit of exposed cam between the pulley and the cam carrier's front seal. The first marks were grooves cut around the cam, none, one, or two grooves. Later, the grooves gave way to a series of numbers stamped around the shaft.

No mark = C-cam, the J-H OEM cam, 272° duration, 0.340" Lift, 110 MOP. This was also the original Lotus cam used for Federal 907 engines.

1 Groove = D-Cam, Orig Lotus Euro 907 cam, 270° Duration, 0.350" Lift, 110 MOP.

2 Grooves = E-Cam, Later Lotus Euro 907 cam, 260° Duration, 0.344" Lift, 102.5 MOP. The 907 was designed by the same motorsports enthusiasts who brought us the berzerker Seven, Elite Mk 14, Elan and Europa, and the Lotus-Ford Twin Cam engine. And they were still in berzerker-mode when they designed it. They did not anticipate that their new customers for the 3rd Generation cars (4-seat Elite-Eclat, and Esprit), would not appreciate having to drive the cars with their foot mashing the throttle to the floor.

When they began to see the light, the E-cam was their first attempt to make the 907 more mild, with a stronger low-end torque curve... at the expense of top-end, balls-out power. It's the same design philosophy use in the later 107 cam, but the E-cam was a smaller step in the mild/ torque cam direction. The 107 took the idea further.

7777777... stamped all around the cam = 107-cam, 912LC & 910 cam, 252° Duration, 0.378" Lift, 104 MOP. This cam goes even further in the direction of improving low-end torque and driveability in commuter traffic, but at further expense of top end power. A 9XX engine with two 104 cams will still reach redline, eventually, but it clearly starts to run out of breath above 5000 rpm... definitely above 5500 rpm.

4444444... stamped all around the cam = 104-cam, 912HC Intake cam (along with 107 on exhaust), 272° Duration, 0.410-0.420" Lift, 104 MOP, 64 Overlap.

5555s, 6666s & 88888s indicate the 105, 106 & 108 competition cams that are not appropriate for street use.

The trouble is that a lot (most) of the non-stock cams now found in 907s are re-ground. Some vendor took an original C-cam and re-ground it to meet E-cam, 107 or 104 specs. And most of them didn't bother to alter or add an identifying mark. You really can't tell just by looking what it is. In that case, measuring the "Lift" will give you some clue whether the cam is stock, or something else. If something else, then does it match the lift given for one of the other 'Lotus' cams given above. If not, and it's a totally different aftermarket grind, then your guess is as good as mine.

*~*~*
Early on, Lotus used one part number for all cams, but with a different Alpha prefix identifying each cam... hence the C-cam, D-cam, E-cam naming. Later, Lotus changed the part number format, and each cam got it's own discrete part number, and the common name became the last 3 digits of the 'serial number' portion of the part number... ie, 104 & 107 cams. The fact that the 104 cam also has a 104 MOP is purely coincidental. The C-cam, etc, also got new part numbers, but the fans still use the old alpha-names.

(Snip).... The Notes to the bottom left are:
Here's your notes with some info added:
RED DOT ....... 110 MOP = design correct MOP for C-cam & D-cam
BLUE DOT ...... 100 MOP = Federal emissions timing for C-cam & D-cam
YELLOW DOT .. 102.5 MOP = design correct MOP for E-cam.
GREEN DOT .... 104 MOP = design correct MOP for 104 & 107 cams

EUROPEAN SPECS .. INlet ....... 102.5 ATDC .. YELLOW Dot
............................. EXhaust .. 102.5 BTDC .. YELLOW Dot
That's the yellow-dot pulleys for the early Euro 'torque' cam, the E-cam.

NORTH AM SPECS .. INlet ....... 100 ATDC ..... BLUE Dot
............................. EXhaust ... 110 BTDC .... RED Dot

That's the red-blue dot, dual-MOP pulleys for the Federal emissions 907s, with the C-cam. The Red-Blue pulleys could also be used to time the D-cams to 110 MOP.

Regards,
Tim Engel

Last edited on 07-11-2017 05:29 am by Esprit2

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qwerty wrote:
Tim wrote:
> If the cams are stock, and the pulleys are 110/100 (97),
> then the best cam timing to use is 110 IN and 100 EX.
> 100 (97) and 115 were emissions settings, and results in a loss of power compared to 110 IN/110 EX.

Is that a typo Tim, should that read 110 IN /110 EX?

Yes, that was a typo, thanks for catching it. I've edited my original message to correct that error.

The best timing for the stock OEM J-H C-cams is 110 IN / 110 Ex.

Sorry about any confusion that may have caused.

Regards,
Tim Engel

Last edited on 10-10-2016 07:58 pm by Esprit2

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subwoofer wrote:
You have both cams installed with Red Dot (110MOP) as the valid timing mark, but if I am not much mistaken they have been timed one tooth advanced (if the white marks are anything to go by). -- Joachim
Peter/ qwerty,
Your photos of the pulleys leave us guessing about how the cams are actually timed. It would be very helpful if you would turn the crankshaft clockwise (as you look at the front of the engine) until it's at Top Dead Center (TDC). Then post another photo of the two pulleys together, so we can see which dots align, and how well they align.

If the cams are stock C-cams, then it would be best for the two red dots to end up aligned when the crank is at TDC.

Regards,
Tim Engel

Last edited on 10-11-2016 05:57 am by Esprit2

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qwerty wrote:
(Snip)... Maybe it does have non standard cams, as yet i do not know. Maybe it's to let the DHLA 45's breathe.Remove a cam cover and measure a cam lobe. First, measure the total egg-shaped height with a caliper. Then measure 90 degrees to the first measurement, in order to get the base circle diameter... the round part at the bottom of the lobe. Subtract the two measurements, and the remainder is the total 'Lift'. The stock J-H C-cams had 0.340" lift. It may have worn down a bit through the decades, but anything radically different, especially 'greater', might indicate the cam is not stock.

The DHLA 45s will breath just fine with 110IN/ 110EX timing on stock C-cams. Both Dellortos (stock J-H 40s, or Lotus 45s) are wasted on either of the emissions MOPs (100 or 115). Performance carbs on tame emissions timing... they're polar opposite goals.

Regards,
Tim Engel

Last edited on 10-10-2016 08:49 pm by Esprit2

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qwerty wrote:
Thinking out loud here, Could this be the end result of the Aux pulley being out by 1 or more teeth and correcting for it?No, it shouldn't. When the timing belt is installed, aligning the cam pulley timing dots, and aligning the aux pulley are two separate activities. Address each one separately, and get each one correct. But making a change to the cam timing should not affect the aux pulley timing, "IF" you pay proper, separate attention to the aux pulley.

All too often, people put paint marks on the old belt that align with similar paint marks applied to the pulleys. Then transfer those marks to the new belt and install it the same way. All that does is preserve the old timing, even if it was wrong. And then, if a subsequent change is made to the cam timing without paying separate attention to preserving the aux pulley timing, then yes, changing cam timing could result in changing the aux timing. But that's because the cams and aux were not treated as separates and timed separately; and NOT because there is some sort of "physics" connection between cam and aux timing. They're separate, treat them separately.

I strongly recommend not marking/ transferring marks when installing a new belt. It is not difficult to time the engine, both cams and aux pulley/ distributor, from scratch. Do it right each time, and don't just transfer previous mistakes.

Regards,
Tim Engel

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qwerty wrote:
I will be taking the cam covers off later this week or on the weekend. I will look for markings.The cam's ID marks are 'outside' of the cam carriers, on the exposed bit between the pulley and the carrier's front lip seal. The only marking on the part of the cam that is inside of the carrier are cast into the cam, not stamped or machined into it. All the cams are cut on the same cast blank, so they will all have the same part number cast into them. That's the blank's part number, not the finished cam's.

The C-cam has no cut grooves or stamped numbers as ID marks. It's the one odd-ball. If your cams are stock originals, then there are no ID marks to find. But finding that out is worth the looking.

Regards,
Tim Engel

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qwerty: "I'm sure he knew that the 110/110 timing was correct for the engine without emissions and is why the white marks have piqued my interest"

Tim: I believe the white marks are there on the cams to check Ignition Timing with a timing light.

If you turn the Engine to TDC I bet the red dots line up. With the engine running at 1k (25D Distributor), check the ignition timing at the crank pully, it is usually set around 8 to 12 degrees BTDC. Now check the cam white marks with a timing light, they probably line up. If they don't, they may indicate maximum advance at higher rpms, in which case they will line up when viewed with a timing light at 2,500-3000 rpm.
Hope this helps. Take care all.

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Tim Murphy wrote:
(Snip)... With the engine running at 1k (25D Distributor), check the ignition timing at the crank pully, it is usually set around 8 to 12 degrees BTDC. Now check the cam white marks with a timing light, they probably line up. If they don't, they may indicate maximum advance at higher rpms, in which case they will line up when viewed with a timing light at 2,500-3000 rpm.I'm not getting my head around that. The ignition fires before TDC, which would require the white marks to be clockwise from the red dots, not counter-clockwise... ie, leading the red dots, not following them. The white marks are on the wrong side of the red dots to be used for checking 'advanced' ignition timing... or I'm totally screwed-up.

Regards,
Tim Engel

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My apologies on the placement of the markings, memory was off apparently and I trust Tim to be right on this matter. If your cam covers are reasonably oil tight and valve clearances have been checked in the not too distant past, leave the covers in place.

I don't buy the white dots for spark timing theory either, I agree with Tim that for that purpose the white dots would lead the red dots, just as he says. But why would anyone use the cam wheels for timing reference? The crank pulley is clearly marked for that exact purpose.

--
Joachim

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I was wrong with the idea that the white marks would be used to with a timing light to confirm ignition/cam timing. I am sorry and a little embarrassed. For some reason, I was thinking the engine ran counter clockwise.

qwerty, have you turned the engine to TDC (top dead center). If so, what marks line up on the cam pully?

Hopefully, I will then keep quiet and let the other, more knowledgeable guys offer help :<)

Last edited on 10-11-2016 10:29 am by Tim Murphy

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Esprit2 wrote: qwerty wrote:
(Snip)... I doubt is has a different Cam but i will check ...how do i check?
On the stock, OEM cams, there were marks on the bit of exposed cam between the pulley and the cam carrier's front seal. The first marks were grooves cut around the cam, none, one, or two grooves. Later, the grooves gave way to a series of numbers stamped around the shaft.

No mark = C-cam, the J-H OEM cam, 272° duration, 0.340" Lift, 110 MOP. This was also the original Lotus cam used for Federal 907 engines.

1 Groove = D-Cam, Orig Lotus Euro 907 cam, 270° Duration, 0.350" Lift, 110 MOP.

2 Grooves = E-Cam, Later Lotus Euro 907 cam, 260° Duration, 0.344" Lift, 102.5 MOP. The 907 was designed by the same motorsports enthusiasts who brought us the berzerker Seven, Elite Mk 14, Elan and Europa, and the Lotus-Ford Twin Cam engine. And they were still in berzerker-mode when they designed it. They did not anticipate that their new customers for the 3rd Generation cars (4-seat Elite-Eclat, and Esprit), would not appreciate having to drive the cars with their foot mashing the throttle to the floor.

When they began to see the light, the E-cam was their first attempt to make the 907 more mild, with a stronger low-end torque curve... at the expense of top-end, balls-out power. It's the same design philosophy use in the later 107 cam, but the E-cam was a smaller step in the mild/ torque cam direction. The 107 took the idea further.

7777777... stamped all around the cam = 107-cam, 912LC & 910 cam, 252° Duration, 0.378" Lift, 104 MOP. This cam goes even further in the direction of improving low-end torque and driveability in commuter traffic, but at further expense of top end power. A 9XX engine with two 104 cams will still reach redline, eventually, but it clearly starts to run out of breath above 5000 rpm... definitely above 5500 rpm.

4444444... stamped all around the cam = 104-cam, 912HC Intake cam (along with 107 on exhaust), 272° Duration, 0.410-0.420" Lift, 104 MOP, 64 Overlap.

5555s, 6666s & 88888s indicate the 105, 106 & 108 competition cams that are not appropriate for street use.

The trouble is that a lot (most) of the non-stock cams now found in 907s are re-ground. Some vendor took an original C-cam and re-ground it to meet E-cam, 107 or 104 specs. And most of them didn't bother to alter or add an identifying mark. You really can't tell just by looking what it is. In that case, measuring the "Lift" will give you some clue whether the cam is stock, or something else. If something else, then does it match the lift given for one of the other 'Lotus' cams given above. If not, and it's a totally different aftermarket grind, then your guess is as good as mine.

*~*~*
Early on, Lotus used one part number for all cams, but with a different Alpha prefix identifying each cam... hence the C-cam, D-cam, E-cam naming. Later, Lotus changed the part number format, and each cam got it's own discrete part number, and the common name became the last 3 digits of the 'serial number' portion of the part number... ie, 104 & 107 cams. The fact that the 104 cam also has a 104 MOP is purely coincidental. The C-cam, etc, also got new part numbers, but the fans still use the old alpha-names.

(Snip).... The Notes to the bottom left are:
Here's your notes with some info added:
RED DOT ....... 110 MOP = design correct MOP for C-cam & D-cam
BLUE DOT ...... 100 MOP = Federal emissions timing for C-cam & D-cam
YELLOW DOT .. 102.5 MOP = design correct MOP for E-cam.
GREEN DOT .... 104 MOP = design correct MOP for 104 & 107 cams

EUROPEAN SPECS .. INlet ....... 102.5 ATDC .. YELLOW Dot
............................. EXhaust .. 102.5 BTDC .. YELLOW Dot
That's the yellow-dot pulleys for the early Euro 'torque' cam, the E-cam.

NORTH AM SPECS .. INlet ....... 100 ATDC ..... BLUE Dot
............................. EXhaust ... 110 BTDC .... RED Dot
That's the red-blue dot, dual-MOP pulleys for the Federal emissions 907s, with the C-cam. The Red-Blue pulleys could also be used to time the D-cams to 110 MOP.

Regards,
Tim Engel

Tim, this is text book "wealth of information" I very much appreciate the effort you went to in explaining this, and if you "OK" the AutoCad drawing, i will update it with your appendments and post for future reference or lurkers. Thank you!

Please see my next posts as i think the mystery or lack thereof solved as i lubed the bores enough to rotate the engine to cam timing at TDC which aligned with the Red Dots after all.

My appologies for the confusion.
Regards
Peter

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Esprit2 wrote: subwoofer wrote:
You have both cams installed with Red Dot (110MOP) as the valid timing mark, but if I am not much mistaken they have been timed one tooth advanced (if the white marks are anything to go by). -- Joachim
Peter/ qwerty,
Your photos of the pulleys leave us guessing about how the cams are actually timed. It would be very helpful if you would turn the crankshaft clockwise (as you look at the front of the engine) until it's at Top Dead Center (TDC). Then post another photo of the two pulleys together, so we can see which dots align, and how well they align.

If the cams are stock C-cams, then it would be best for the two red dots to end up aligned when the crank is at TDC.

Regards,
Tim Engel

Tim,

Today i had the chance to get the bores ready to rotate the engine to TDC and as you can see by the photos it is in fact timed to 110 / 110. My appologies for the confusion. The mystery is solved and the white marks debunked. I will erase them.

I will post 4 pictures: two at red dot alignment and crank mark sitting at TDC and another two with the white marks and crank mark sitting at 2x past TDC

My appologies for the confusion to all and feel free to delete certain posts as to not cause confusion for future reference. We all gained from the informative response you gave in response. (i'm a glass is half full person).


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Esprit2 wrote: qwerty wrote:
(Snip)... Maybe it does have non standard cams, as yet i do not know. Maybe it's to let the DHLA 45's breathe.Remove a cam cover and measure a cam lobe. First, measure the total egg-shaped height with a caliper. Then measure 90 degrees to the first measurement, in order to get the base circle diameter... the round part at the bottom of the lobe. Subtract the two measurements, and the remainder is the total 'Lift'. The stock J-H C-cams had 0.340" lift. It may have worn down a bit through the decades, but anything radically different, especially 'greater', might indicate the cam is not stock.

The DHLA 45s will breath just fine with 110IN/ 110EX timing on stock C-cams. Both Dellortos (stock J-H 40s, or Lotus 45s) are wasted on either of the emissions MOPs (100 or 115). Performance carbs on tame emissions timing... they're polar opposite goals.

Regards,
Tim Engel

Quite a few replys to get through!!, Once i have the covers off i will measure the lift will dial guage. PS i checked yestrday for markings on the exposed camshaft - Looks like a standard as no markings at all.

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Esprit2 wrote: qwerty wrote:
Thinking out loud here, Could this be the end result of the Aux pulley being out by 1 or more teeth and correcting for it?No, it shouldn't. When the timing belt is installed, aligning the cam pulley timing dots, and aligning the aux pulley are two separate activities. Address each one separately, and get each one correct. But making a change to the cam timing should not affect the aux pulley timing, "IF" you pay proper, separate attention to the aux pulley.

All too often, people put paint marks on the old belt that align with similar paint marks applied to the pulleys. Then transfer those marks to the new belt and install it the same way. All that does is preserve the old timing, even if it was wrong. And then, if a subsequent change is made to the cam timing without paying separate attention to preserving the aux pulley timing, then yes, changing cam timing could result in changing the aux timing. But that's because the cams and aux were not treated as separates and timed separately; and NOT because there is some sort of "physics" connection between cam and aux timing. They're separate, treat them separately.

I strongly recommend not marking/ transferring marks when installing a new belt. It is not difficult to time the engine, both cams and aux pulley/ distributor, from scratch. Do it right each time, and don't just transfer previous mistakes.

Regards,
Tim Engel

This is my intention.

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First the red Dot Alignment on the cam Pulleys...

Attachment: 110 IN & 110 EX.JPG (Downloaded 68 times)

qwerty
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...and the corresponding crank mark

Attachment: 110 IN 110 Ex at Crank.jpg (Downloaded 67 times)

qwerty
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White Marks - Cam

Attachment: White Marks.JPG (Downloaded 68 times)

qwerty
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...and white marks at Crank

Attachment: White Marks at Crank.JPG (Downloaded 65 times)

qwerty
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So after all that, the engine is indeed timed at 110 / 110.

My sincerest appologies for all that causes confusion.

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Just checked the back of the cam gears and there's a black mark....


....JUUUUUUST KIDDDING!!

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Tim Murphy wrote: I was wrong with the idea that the white marks would be used to with a timing light to confirm ignition/cam timing. I am sorry and a little embarrassed. For some reason, I was thinking the engine ran counter clockwise.

qwerty, have you turned the engine to TDC (top dead center). If so, what marks line up on the cam pully?

Hopefully, I will then keep quiet and let the other, more knowledgeable guys offer help :<)

No embarrassment warranted Murph. Thanks for the lateral thinking.

Last edited on 10-11-2016 04:03 pm by qwerty

Esprit2
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Tim Murphy wrote:
Hopefully, I will then keep quiet and let the other, more knowledgeable guys offer help :<)Discussion is good, don't go silent on us.

Regards,
Tim Engel

Esprit2
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qwerty wrote:
Just checked the back of the cam gears and there's a black mark....

....JUUUUUUST KIDDDING!!
Keep that up and we'll make you go sit in the corner.
;-)

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You may as well, it's like 90 degrees over here....

...sorry I couldn't resist. :)

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Just starting cam belt/tensioner replacement on B74 2 5757

When camwheel marks face each other, intake notch is 110 and exhaust notch is 115

I've heard the engine run, and it sounded fine, but haven't driven the car (15615) yet

Should I time it back to 110/110 when I put the belt on?

Esprit2
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Does your car have to pass a strict emissions test. If so, it will have a better chance with 115 In / 115 Ex cam timing.

If the local emissions standard is a little more lax, or if your car, being rather old, doesn't have to be tested, then the engine will run better if the standard cams are timed to 110 IN / 110 Ex. It also helps to dial-in a little more static ignition advance at around 12* BTDC, and a richer mixture will also help performance.

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Thanks! No emission test for this car, classic plates and insurance obviates that in AZ.

Will time back to 110/110. I was just checking in here to be sure that the 110/115 timing wasn't some "hot tip" that was somehow "better" than the stock setting.

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If you want to play with cam timing, give 104 In / 110 Ex a try. But for that, you'll need to buy a 104 pulley. If you just want to use the best option available on your stock pulleys, then it's 110 In / 110 Ex.

Regards,
Tim Engel



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