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cams, valve timing and ignition timing  Rating:  Rating
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 Posted: 10-10-2016 06:56 pm
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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 06:58 pm by Esprit2

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 Posted: 10-10-2016 07:07 pm
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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 04:57 am by Esprit2

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 Posted: 10-10-2016 07:24 pm
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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 07:49 pm by Esprit2

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 Posted: 10-10-2016 07:38 pm
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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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 Posted: 10-10-2016 07:46 pm
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Esprit2
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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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 Posted: 10-11-2016 12:21 am
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Tim Murphy
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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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 Posted: 10-11-2016 04:53 am
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Esprit2
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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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 Posted: 10-11-2016 05:36 am
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subwoofer
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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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 Posted: 10-11-2016 09:27 am
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Tim Murphy
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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 09:29 am by Tim Murphy

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 Posted: 10-11-2016 09:47 am
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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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 Posted: 10-11-2016 10:02 am
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qwerty
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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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 Posted: 10-11-2016 10:04 am
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qwerty
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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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 Posted: 10-11-2016 10:08 am
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qwerty
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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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 Posted: 10-11-2016 10:20 am
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qwerty
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First the red Dot Alignment on the cam Pulleys...

Attachment: 110 IN & 110 EX.JPG (Downloaded 66 times)

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 Posted: 10-11-2016 10:21 am
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...and the corresponding crank mark

Attachment: 110 IN 110 Ex at Crank.jpg (Downloaded 65 times)

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 Posted: 10-11-2016 10:25 am
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White Marks - Cam

Attachment: White Marks.JPG (Downloaded 66 times)

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 Posted: 10-11-2016 10:25 am
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...and white marks at Crank

Attachment: White Marks at Crank.JPG (Downloaded 63 times)

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 Posted: 10-11-2016 10:33 am
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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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 Posted: 10-11-2016 10:35 am
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qwerty
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Just checked the back of the cam gears and there's a black mark....


....JUUUUUUST KIDDDING!!

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 Posted: 10-11-2016 10:46 am
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qwerty
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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 03:03 pm by qwerty

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