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Cam Gears - Got any available?  Rating:  Rating
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 Posted: 04-30-2005 12:50 am
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Ron Earp
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Anyone got any 100 degree cam gears they'd like to sell?  I've checked with Dave Bean, Delta, JHPS, and JAE but all of them are "between gear sets right now" or don't have them.  I'd like to have a set to swap in on the dyno and see if it changes anything.  I'm still some weeks away from that, but thought I'd ask now.  No, I can't use adjustable gears or I'd be doing it - I wish!  Thanks much!!!! 

Ron

Last edited on 04-30-2005 12:51 am by Ron Earp

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 Posted: 04-30-2005 08:08 pm
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Jensen Healey
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Were there any 100^ cam gears? The later Esprits must have had appropriate gears for their 107 and 104 cams which IRRC were set at 104 degrees. Since the gear has 40 teeth and each tooth is 9^,  use the 115 marks and move one tooth to 106 and use an offset dog to get to 104.

Speaking of cams, I have just acquired a pair of cams that have 7777777 marked around one end. I assume these are the REAL 107 cams from Lotus. Can anyone confirm?

I have also come into possession of Engine # B74 04 6951 along with the front suspension, 4 speed transmission, spare head, cam carriers, and 6 road wheels, some of which are shod with Yokohama AVS T-60s.

Kurt

Last edited on 04-30-2005 08:09 pm by Jensen Healey

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 Posted: 04-30-2005 11:17 pm
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Judson Manning
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Kurt,

I have a set of cams with the 777777 marking, but in another thread I've asked Greg Fletcher for the specs on the 107 cams available through JHPS.

My set measures out to 0.388" total lift and 272^ total duration measured (as best I could) at zero lift.  There are other '107' cams out there that measure closer to 252^ total duration (I think these cams are a later variant used in the Turbo Esprits).

I'm afraid that like the JH cams, there may be many factory 'flavors' of the 107 cam out there not to mention the various aftermarket grinds.

What are the specs on your cams?

Judson

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 Posted: 04-30-2005 11:23 pm
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Jensen Healey
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How do I measure the duration if the cam is lying on the workbench?

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 Posted: 04-30-2005 11:57 pm
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Mark Rosenbaum
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Using a cam carrier as a holder, you could bolt a degree wheel to the front of the cam, then gin up a rigid fixture that would place a dial indicator's tip in contact with the cam lobe.  Rotate the cam and note the degree wheel marking when the dial indicator first rises to 0.050" above the heel of the cam, and when it drops to 0.050" on the other side of the lobe.  The cam duration is the difference between the two degree readings.  (Note that some cam manufacturers spec their cams at zero lift instead of 0.050" lift, and you can expect a difference of 20 to 30 degrees between measurements made at the two sets of points.)

Finally, since the cams turn at half the crankshaft rate, and everything automotive is based on crankshaft degrees, you would double whatever duration you get in this test before comparing your figures to the published ones.

Given the fact that there are so many different Lotus and JH cams around, I'd think it prudent for anyone building a performance engine to verify each cam's duration with a test of this sort.

Last edited on 04-30-2005 11:58 pm by Mark Rosenbaum

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 Posted: 05-01-2005 12:08 am
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Judson Manning
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The lift is easy enough:  Lobe Height - Base Circle

I just found an old set of notes that suggest the other 'flavor' of 107 cams has a total lift of 0.378" and total duration of 252^.  Since my 'flavor' has 0.388", this may be an easier way of determining what you have.

Duration is a bit more involved as the cam needs to be installed in a cam tower with a bucket (or some other way to measure displacement), and you will need a degree wheel and a set of calipers.

Getting reliable and accurate measurements is very dificult.  Start by measuring duration from something easy like 0.050" lift, then from 0.025" and so on until you get a good feel for what the duration is at 0.000" lift.

My 107 cams measure 224^ @0.050" lift vs. 272^@0.000" lift which is exactly the same measurement I got for a set of stock JH cams which have total lift of 0.340".

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 Posted: 05-01-2005 11:55 am
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Ron Earp
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Judson,

According to Jeff at JAE and some fellow at Dave Bean, there are 100, 102.5, 104, 107, 108, 110, 112.5's available in the trapizoidal drive for the JH. But, both only had a couple of the more common ones available and not the 100 or 102.5. It really doesn't matter a lot for me which I use right now, but if I had a set I'd put them on while everything is out.

Ron

Last edited on 05-01-2005 11:56 am by Ron Earp

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 Posted: 05-01-2005 07:15 pm
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Esprit2
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Lotus Cams

Cam ID ..........  Duration........  Lift......  Overlap...  MOP

C or 101 cam......  272° ........ .340" .....  52° ......  110° / Red dot

D or 102 cam......  270° ........ .350" .....  50° ......  110° / Red dot

E or 103 cam......  260° ........ .344" .....  55° ......  102.5° / Yellow dot

107 cam.............  252° ........ .378" .....  44° ......  104° / Green dot

104 cam.............  272° ........ .410" .....  64° ......  104° / Green dot

DS-2 Cam...........  280° ........ .415" .....  72° ......  104° / Green dot

The C-cam is the stock J-H cam

Comparisons by the numbers alone are difficult.   The E,  107, 104  and DS-2 cams all use much more aggressive opening and closing ramps.   The seat to seat durations may not be too impressive,  but their effective open times are better than some cams quoting significantly longer durations.   Compared to the C & D cams,  they are all performance improvements.

The E-cam addressed the 907's  "torqueless wonder" reputation.   The milder timing produced a noticeable improvement in low end torque,  while the more aggressive ramps and higher lift kept top end horsepower the same (usually you trade one for the other).   No more power,  but the torque made the car easier to drive in traffic and it "felt" more powerful.

The 107 is the "Turbo" cam.   Forced-induction engines don't like a lot of overlap since it's hard to force-feed the cylinder when the back door is open.   However,  they do like lift.   In a naturally aspriated engine,  the higher lift really pays off.   The cam gives an even stronger bottom end than the E-cam plus a mild increase in top end power.   The useable power band is wider so the car is easier to drive in traffic.   A good street cam,  but not a hot-rod or track cam.

The 104 cam gets back to the C-cam's duration,  but with the aggressive ramps and much higher lift.   This is a good street-performance cam,  however the top end performance does come at the expense of low end torque.   Overall,  performance is way up...  just don't get caught in the wrong gear at low speeds.   Great in the torquey 2.2,  but not everyone's cup of tea in the torqueless 2.0.   I've got a pair of 104's in a 2.0,  4-seater Lotus Eclat and have no problem with it.

The DS-2 by Dave Smith is similar in character to the 104,  just more of the same.   I've got a pair of them in a 2.2-907 Esprit S2.   Great street performance cams when combined with the 2.2's torque.

The Excel SE & SA  and the Esprit S3 HC  (2.2 912 HC)  used a 104 cam on the Intake and a 107 cam on the exhaust.   That was a compromise set-up that gave some top end improvement without sacrificing anything on the bottom end.

Tim Engel

 

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 Posted: 05-02-2005 02:50 am
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Jensen Healey
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I have just discovered a pair of cam pulleys that are marked 110 and 100 in the spares mentioned earlier. There are also some other marks, a D and an F (with hash marks) opposite the regular marks.

I am considering using the 100^ pulleys with the 'hot' cams I acquired.

Welcome to the board Tim!

 

Kurt

JH 13148

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 Posted: 05-02-2005 12:27 pm
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Brian Kelly
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Just for grins I thought I’d list my Paeco Cam Grind Spec.  This is what they put in their Stage II modified.

 

Timing: Intake 44/76, Exhaust 80/40, Duration 300, Overlap 84, Lift 0.370”

 

Also: 11:1 compression, Dellorto 45’s.

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 Posted: 05-02-2005 12:48 pm
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Judson Manning
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Ron,

If I'm read the IT rules correctly, I think you may be stuck using the cam timing that was available with the car as delivered (i.e.  the workshop manual lists 3 sets:  Mk1, MkII and later JH5 w/ emissions cams).

While other cam gears may be available, I think if you ever got called on it, the scrutineers would look at the published valve opening and closing time listed in the workshop manual.

Alternatively, I've never seen an 'official' JH workshop manual that ever listed the lift spec on the cam.  Therefore, while everyone may 'think' the stock JH cam has a 0.340" lift, none of us in fact may be correct... 

Judson

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 Posted: 05-02-2005 01:17 pm
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Judson Manning
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Tim,

How about specs for the N/A Esprit 2.2?  My 107 cam specs differ from the 107 specs you listed, and I think they may be an earlier version.

While it's possible they could be regrinds, my first set came from DBE and were non-touched-up, 'pull-outs'.   I later shattered one of those cams when I lost a timing belt.  One call to JAE and they found a replacement on the shelf with exactly the same specs.

Ron,

Now that I've had a chance to check my notes, I think you're referring to the cams available for North American engines after engine #10480.  Intake does indeed have 100^MOP and exhaust has 112.5^MOP.  However, the exhaust does lose 5^ in duration (CA emissions, Jensen GT?).  I'll check around, but I think our friends in CA may be the best source for this variant.

Sorting Lotus part-numbers is just like Forrest Gump...you never know what you're going to get!

 

 

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 Posted: 05-02-2005 02:10 pm
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Mark Rosenbaum
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Judson, if the figures you're quoting for post-10480 cams are from the shop manual, General Specifications pg. 2, then it's my understanding that the exhaust cam timing shown as 66 BBDC / 21 ATDC is a typo, and that the correct figures are 66 BBDC / 26 ATDC.  According to section A52 of the shop manual, and service bulletin 75-9, engines 10480-up were timed at 100 IN / 110 EX using the appropriate gears.

Also, in regard to cam lift -- I don't find any sources that list either maximum lift, or the lift at which the cam timing is measured.  So one could perhaps argue to a scrutineer that a cam with any maximum lift was therefore acceptable, and that the specified 272^ duration occurred at, say, 0.050" rather than the zero lift, provided the cam manufacturer specified it that way.... 

Just a thought.

Last edited on 05-02-2005 02:26 pm by Mark Rosenbaum

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 Posted: 05-02-2005 07:03 pm
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Esprit2
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Judson Manning wrote: Tim,

How about specs for the N/A Esprit 2.2?  My 107 cam specs differ from the 107 specs you listed, and I think they may be an earlier version.

While it's possible they could be regrinds, my first set came from DBE and were non-touched-up, 'pull-outs'.   I later shattered one of those cams when I lost a timing belt.  One call to JAE and they found a replacement on the shelf with exactly the same specs.

Judson,

The Esprit S2.2 used two 107 cams while the S3 used a 104 on the intake and a 107 on the exhaust.   The cam data I quoted above is right out of the Lotus manuals.

50° BBDC  Exhaust Opens

22° ATDC  Exhaust Closes

22° BTDC  Intake Opens

50° ABDC  Intake Closes

252° Duration,  44° Overlap,  0.378" Lift

What timing data do you have for the 107 cam?   In the book,  "The Third Generation Lotus...",  the author quotes the Turbo cam as being  265° Duration,  55° Overlap,  105 MOP  and  0.380" lift  (57.5,  27.5,  27.5  57.5).   However,  I've never seen a reference to such a cam in a Lotus manual.   The only thing I can think of is that the original Turbo Esprit was introduced in the UK and Europe a few years before it came to the US in 1983.   For '83,  the car was substantially re-engineered and the engine used two 107 cams for all markets.   What were the pre-83 Turbo cams?...   I don't know.   But if the timing was substantially different than quoted above for the 107,  then it was a different cam entirely.   The 107 didn't evolve...  it was what it is.

Lotus quotes cam duration as seat to seat.   I've never seen that written anywhere,  but I've played Lotus for a long time and that's the way I've always found their cams to be.

Later,     Tim Engel

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 Posted: 05-02-2005 08:01 pm
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Esprit2
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Mark Rosenbaum wrote: Judson, if the figures you're quoting for post-10480 cams are from the shop manual, General Specifications pg. 2, then it's my understanding that the exhaust cam timing shown as 66 BBDC / 21 ATDC is a typo, and that the correct figures are 66 BBDC / 26 ATDC.  According to section A52 of the shop manual, and service bulletin 75-9, engines 10480-up were timed at 100 IN / 110 EX using the appropriate gears.

All the cam timing specs listed in General Specifications,  pg 2 are for the same cam...  what Lotus called the "C" or 101 cam (Cam ID numbers like 101,  104,  107 refer to the last three digits of the Lotus part number).   The different timing events listed result from installing different MOP pulleys on the cams.

The middle data set for engines from 4030 represents the nominally correct C-cam timing with two proper 110 MOP pulleys.

The third data set for engines prior to engine 4030 is with 115 MOP pulleys on both cams.   The 21, 71, 71, 21 timing noted there is correct.

The upper data set for engines after 10480  reflects a correct 110 MOP pulley on the intake cam and a 115 MOP pulley on the exhaust cam,  advancing it 5 degrees.   That changes the exhaust cam's 66 BBDC opening / 26 ATDC closing  to  71 / 21.   The manual indicates 66 / 21 and would be a typo for that combination.

However,  as Mark notes,  on page A52,  the manual contradicts itself by stating that the cams on engines after 10480 are timed to 100 MOP / 110 MOP.   I'm a Lotus guy and not into J-H enough to say which page is correct.   But I can say that pg A52 agrees with the Federal Emissions Lotus 907 settings...   100/110.

A 907 with C-cams will run best overall when timed at 110/110.   Everything else is a compromise for one purpose or another.   For Lotus,  the 100/110 timing was used on emissions engines.   Advancing the intake cam 10 degrees increased overlap by a like amount.   That allowed a little more exhaust gas dilution in the intake charge with a result similar to exhaust gas recirculation...  it lowered the oxides of nitrogen and they didn't have to develop an EGR system.

It also gave a little more top end horsepower at the expense of low end torque.   Horsepower sells cars.   The lean carb and retarded ignition timing settings used on the emissions engines really sapped the power,  and this got some of it back.   At least on paper.    However,  the 2.0 907 never had much low end torque and really couldn't afford to give up any in the quest for more top end power.   So the car was even weaker off the line and in traffic...  it wasn't much fun to drive at anything less than full scream.

For a street car,  set the C-cams to 110/110,  static ignition timing to 14-16 BTDC and adjust the idle mixture for a strong idle.

On a wide open track with long straights,  top end power might be more important.   In that case advancing the intake cam alone might be worth it.   The 104,  102.5  and 100 MOP pulleys will all advance the intake cam.   Or advance the intake a bit and retard the exhaust a bit.   104 MOP pulleys on both cams will advance the intake 6,  retard the exhaust 6,  and increase overlap 12.   That would be a poor man's 104 cam timing without the increased lift and aggressive lobe ramps.

Remember,  changes to MOP affect the two cams in opposite ways...

A larger MOP advances the exhaust and retards the intake.

A smaller MOP retards the exhaust and advances the intake.

Later,    Tim Engel

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 Posted: 06-14-2005 12:19 am
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Ron Earp
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Judson and Tim,

Cams might be open for the little JH.

BMW's are pulling a scam in IT right now. Their factory shop manual has no cam specs, so, some have taken that to mean that cams are free. As such, two weeks ago at CMP a stock BMW cylinder head and cams were lying on the tech table when you check in.

Guess what? The top two BMWs in the SE didn't run at CMP. They went home. So, something is up.

So, a cam with the same duration, that is listed in the manual, but good lift might could be used. A 104 would probably get the job done and basically mimic (close enough for old car specs) the JH cam profile but give better lift.

All for the future. Right now I just want to get this thing started, the suspenion aligned, and out driving about!

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 Posted: 06-14-2005 03:15 pm
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Judson Manning
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Ron, I think you have the right idea...let's get the car on the track, sorted and start having fun.  Worry about what the scrutineers when you get that podium finish!

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