Lotus Elan

kent L2 cam fitting or not?

PostPost by: vxah » Tue May 23, 2017 12:44 pm

I am just in the process of doing the 1000 mile engine service on my +2 after a rebuild.
Some time before the rebuild I removed a pair of L2 cams that I had fitted to the engine back in 1984, the thought was that it may run a little better with the stock S130 cams.. Can't say that it did but when I rebuilt the engine with the rest of the car I re-used the S130 cams.
The engine is now re-bored and stroked to 1720cc and runs ok but as I am revisiting the valve gear I thought I would ask if anyone had knowledge of these cams such a build? The head was rebuilt with standard valves etc but it did have some mild porting done back in 84.
I recall the L2's have a little less lift than the S130's but a little more duration? At the time of rebuild I fitted the S130 cams because I understood the TC to like lift not duration? That said I was looking at the L2 lobes recently and thinking that they look as if they have a more aggressive profile possibly meaning more lift earlier on even though the ultimate lift is a little less? Could this be a benefit to my engine? any thoughts?
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PostPost by: collins_dan » Tue May 23, 2017 4:55 pm

I had a set of L2 cams in my S4 which I replaced with a set of QED360 cams (sprint equivalent) and I have to say that I have also been disappointed. I expected more of a torque improvement, but have found them to be just generally less lively. I am planning to have the car tuned on a dyno and will let you know if its the tune or if the L2 cams are just underappreciated. All the best, Dan
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PostPost by: nigelrbfurness » Wed May 24, 2017 8:15 am

I agree with Dan's comment that L2s are underappreciated. Having run L2s and Sprint (D-type) cams in a 1760cc with big valve head, I prefer the L2s and am running with them now. Bags of torque, smooth delivery throughout the rev range, very little "peakiness" above 1500rpm and you never need to rev the engine beyond 6K although it will go on forever if you let it. Sprint cams seem to have a much more defined power band higher up the rev range. I doubt the slight ultimate higher bhp obtainable with Sprint cams is worth the loss in driveability.

Nigel F.
1970 S4SE/1760cc big valve/SA-AX block, L2s, 45DCOEs, 1978 Jensen GT, 1962 AH Sprite, Alfa-Romeo 159, 1966 Bristol Bus, 1947 AEC Regal bus.
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PostPost by: rgh0 » Wed May 24, 2017 10:08 am

Personally I think a 300 degree duration cam like the L2 is to long for a road engine. The dyno says these cam give you good top end power and most of it you cant use as its above 6500 rpm. The dyno also says they have a torque dip in the 3000 rpm range compared to a sprint cam. It does not mean a L2 cam does not work it is just not the best choice IMHO a sprint D cam is also good but also not my choice

For a 6500 rpm engine you certainly dont need to go beyond 290 degrees duration and more likely 280 degrees is the max you need unless you are looking for a very high lift over say 0.41. Lift is what you should be working on not duration.

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PostPost by: Craven » Wed May 24, 2017 12:34 pm

Hi,
Apparently the low end performance is improved by timing peak lift at 106 deg rather than the 102 deg as specified. L2 46/70/70/46 Duration 296 deg Lift 0.345.
FWIW
Ron.
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PostPost by: rgh0 » Wed May 24, 2017 12:41 pm

Yes you can do similar with a 280 to 290 degree cam and get similar torque improvement at the expense of top end power but in the end a shorter duration higher lift cam will work better tuned to its optimum than an L2 when tuned to its optimum.

Running a longer duration inlet ( say 290 degrees) with a shorter duration exhaust ( say 280 degrees) can help with torque while minimizing top end power loss in a 6500 rpm engine. But in the end lift has more impact than playing with fine tuning on the timing so you need to bite the bullet and build a high lift valve train which does not really cost more than a standard lift valve train these days if your doing a rebuild.

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PostPost by: vxah » Wed May 24, 2017 4:20 pm

Thanks for the replies chaps, seems to me that it's probably not worth the effort to be doing as there may not be a clear gain from the swap, least ways not without maybe experimentation with peak opening etc?
Added to the fact that I was likely going to run down to Castle Combe on Saturday!

Julian.
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