Lotus Eclat Elite 907 engine camshaft variations - LotusTalk - The Lotus Cars Community
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post #1 of 3 (permalink) Old 11-01-2017, 03:37 PM Thread Starter
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Question Lotus Eclat Elite 907 engine camshaft variations

Hi everyone,

I just had my Lotus 907 engine rebuilt locally (by Active Engines in Mississauga, Canada) and installed it back in the car. Unfortunately I cannot get it to run smoothly.

After some research, I determined that my issue is likely incorrect timing.

The engine appears to be equipped with the camshafts that have 2 grooves (see picture below, this appears to match camshaft Spec 5 as per the workshop manual). Can anyone confirm that I'm interpreting this correctly? The 2 grooves can be seen clearly between the sprocket and the cam housing.

The matching cam sprockets should have yellow timing dots as per the manual. However, my cam sprockets have the blue/red timing marks on each cam. See pic below. The blue/red timing marks are facing towards the engine (toward the rear of the car).

This would indicate that I've got non-matching camshafts and cam sprockets... can anyone confirm that my findings are correct?

Dave Bean Engineering in California sells adjustable cam sprockets. Would this solve my issue?

Any input would be greatly appreciated - I really need your help.
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post #2 of 3 (permalink) Old 11-02-2017, 04:39 AM
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Can't help with the older 907 engines specifically,

But I DO know that the dots on the cam wheels are on BOTH sides of them.

The dots on the front are the ones that must be timed accurately. (Time to break out Lotus Tool #2, the inspection mirror?)

Further, they were marked IN (intake) and EX (exhaust) so verify that they are installed and timed correctly (as viewed from the front).

I bet that @Esprit2 would be able to help you with more specifics.

On Esprits, the red & blue dots indicated different timing specs (emissions). The Turbo's optimum cam wheels had green dots (104 MOP or Mean Opening Point).
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Atwell Haines / '88 Esprit / Succasunna, NJ USA

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post #3 of 3 (permalink) Old 02-05-2018, 04:30 PM
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This is an old thread... did you ever get it sorted out? Sorry I'm late to the game, but I don't hang out on LotusTalk very much.

2 Grooves does indicate the Euro E-Cam (aka, 103 cam). It's 260 duration, 55 overlap, 0.344" lift, and 102.5 MOP (Maximum Opening Point, aka Lobe Centers). The timing dots on the correct pulleys are Yellow.

On the dual-MOP pulleys you have, the red dot is 110 MOP, and the blue dot is 'called' 100 MOP, but it's really 97. The geometry doesn't support both 110 and 100 co-existing on the same pulley, so they cheated a bit to force-fit the 100 blue dot onto the same pulley.

Compared to where the E-cam wants to be, the red dot pulley would retard the intake 7.5, and advance the exhaust 7.5. The 97 blue dot would advance the intake 5.5, and retard the exhaust 5.5.

The stock cams were 272 duration. They liked to rev and made more top end horsepower when driven in a spirited manner; but many people who bought a 4-seat estate were looking for something a little more civilized, with more low end torque, and easier to drive in traffic. The E-cam was Lotus first, half-step in that direction. The later 107 cam took a bigger step in that direction, and is popular with many Jensen-Healey owners (same engine, but more of a silk scarf/ wicker basket crowd).

So what do you want? A gentleman's estate, or a 4-seat sports car? If you want the milder engine, we can work on sorting out these cams. If you want the top end performance, the E-cams won't give it to you, and you should talk with the shop about replacing the original cams (do you have them, or did they keep them?).

Set the crank to TDC (Top Dead Center). If the cam pulley timing marks end up on the far opposite sides of the cam pulleys, then rotate the crank clockwise (as viewed from the front) one full revolution, and back to TDC. The cam pulley timing marks should now align on the imaginary centerline between the two cams. Snap a clear, well exposed picture of the front side of the cam pulleys, and post it here so I can see the timing marks.

Of the two timing marks facing forward on each pulley, one will be next to an IN mark cast into the pulley spokes, and the other will be next to an EX mark. On the intake pulley, the dot next to the IN mark should align with the dot next to the EX mark on the exhaust cam pulley. And they must align on the imaginary centerline between the cams. If they align, but are high or low, then the cams are NOT correctly timed.

If the dots are aligned on the centerline, then the pulleys are correctly timed. BUT they're the WRONG pulleys (not yellow dot, 102.5 MOP pulleys). You can 'correctly' time the WRONG pulleys all day long, and the cam timing will still be wrong. All this talk about checking the current timing is only to see if the mechanic had some clue what he was doing (he at least got the correct dots aligned). But he still gets failing marks for using the wrong pulleys. The cams are incorrectly timed.

Can you use adjustable pulleys?
Yes. But they don't come pre-set to any MOP, you have to do that. And setting them is a bit of a procedure involving a degree wheel on the crank, dial indicators on the piston crowns and cam lobes, and some idea about what you're doing. If you had to ask if adjustable pulleys can be used, then I'm betting you don't know how to set them up. Is that about right? I would recommend that you just order up a set of Lotus 102.5 MOP pulleys from a UK supplier, like SJ Sportscars, Burton Power, PNM Engineering... etc. You can try JAE and Dave Bean, but I'd be surprised if they had anything for you.

If you post and I don't respond to you right away, PM me. Again, I'm an infrequent participant on LotusTalk.

Tim Engel
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Last edited by Esprit2; 02-12-2018 at 12:25 PM.
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