Lotus Elan

CPL2 Cams true potential

PostPost by: miked » Tue Jun 07, 2011 12:51 pm

I am just putting back together a motor for a Plus 2. PO spent a lot of money. Block and Head at QED within 1000 miles ago. I have only been in to do water pump and front cover problem with chain tensioner thread. Inside is mint, as expected. When I got the car I only did few miles before starting remedial work on the running gear etc. Motor ran very smooth and balanced without any trace of smoke but lacked some punch. It had a noisy Piper Cross air filter box. Lot of Induction noise! Not my cup of tea. Jumbo jet job, sorry! :oops:
I am going back to standard proper cold air box set up and less induction roar.
Head has had porting and balance of combustion chambers. Also large inlet valves. Has had a Skim that renders it almost at big valve head thickness. Tad thicker by a few thou?. Has CPL2 cams. Carbs have 30 chokes, 110 main jets and 155 air correctors etc.
Having read the Mile Wilkins (Lotus twin Cam Engine) pages 46 and 47, I should be looking at nominally 130BHp with this set if I have 33 mm chokes 130 main jets and 170 air correctors. Maybe a bit of a stupid question but I think there is no point in putting the carb?s back as they were. I have the parts and spares to make them to the BRM/big valve spec?. Would anybody disagree that I am better doing that to release the potential of the ?set up?. I have a new Dizzy fitted from QED.
It does look like the intention was BRM 130 BHP spec? but the PO did not fully complete the job. I got the data from history receipts etc, a spec? sheet from a tune guy who overhauled the carbs. I have not split them yet but can see the 30mm chokes are in there.

PS I know there is a lot of science and rolling road stuff behind tuning etc but I need to start somewhere and ?as is? seems to be the wrong place. Any comment/advice welcome
Thanks Mike
Mike

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PostPost by: GrUmPyBoDgEr » Tue Jun 07, 2011 3:09 pm

As far as I can recall, CPL2 cams have a good all round profile with little tendency to idle or low down lumpiness.
Obviously the larger jets will have an overall effect on fuel consumption but is that a worry on a not day to day car?
The bigger chokes must surely, with the matching jets, give a better top end performance?
I'm with your reasoning, all of the spade work has already been done, so go for it.
No point in spoiling the broth for a pinch of salt :D

Cheers
John
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Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
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PostPost by: elanman999 » Tue Jun 07, 2011 4:19 pm

Mike,
As John said they are a good allround cam. When I first fitted them to my +2 I went straight for "Sprint" carb settings and it ran well. I did not have it dynoed in that spec. I did have some trouble with the dizzy but that was because it was very old (knackered). You have that problem solved.
Cheers
John
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PostPost by: david.g.chapman » Tue Jun 07, 2011 6:20 pm

I am running CPL2 cams on my Stromberg engine with a 9.8(ish) to 1 head and slightly richer needles than standard.

Compression pressures are in the 170psi region - I don't know about the power - 120bhp? 130bhp if I had a high compression head.

The engine runs very smoothly and I am a happy bunny.

Dave Chapman.
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PostPost by: miked » Wed Jun 08, 2011 8:27 am

Thanks guys, that is reassuring. I will get the carbs sorted out with the right bits. Head now on and motor going back in tonight.

Thank Mike :D
Mike

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PostPost by: GrUmPyBoDgEr » Wed Jun 08, 2011 9:20 am

I had a mate, Geoff Hill, who won his class nearly every year he competed in the south western sprint & hill climb championship.
His U2 had a Twincam fitted with CPL2's & he swore by them for their smooth delivery of torque & power.
To watch him drive that car was a lesson in control & smoothness of driving; a real treat.
He'd go up those hills as sweet as a nut, in comparison to others with their revvy L1 cam'd motors making a song & a dance of it all the way up the hill.
I'm sure you will be happy with your finished engine.

Cheers
John
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Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
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PostPost by: Dag-Henning » Wed Jun 08, 2011 11:01 am

Believe there is a difference between CPL2 and L2.....Always thought CPL2 was not much more than standard, where as L2 was a "light rally" profile .... (?)
Rohan - have you got some info on the differences ?

Dag
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PostPost by: ardee_selby » Wed Jun 08, 2011 11:18 am

By coincidence I was pondering the same question....

FWIW, Have just been looking at these references....

http://www.kentcams.com/info/catalogue_lowRes.pdf (Page 15)

http://freespace.virgin.net/tommy.sandham/cams.htm

Cheers - Richard
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PostPost by: Dag-Henning » Thu Jun 09, 2011 11:23 am

Yes, as I thought... Guess the L2 corresponds better with the 125-130bhp figures....
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PostPost by: rgh0 » Thu Jun 09, 2011 11:46 am

CPL2 cams = basically a lotus sprint cam by another name = 125 to 130 hp depending on rest of engine detail.

L2 cams = cheap hot up cam, standard cam lift and can use standard valve and spring gear, but longer duration, more top end but poorer mid range. Probably similar or little more power to CPL2 but all at top end.

I believe a better option than either is something like the L14 or QED 420 or similar - short duration around 280 seat to seat and above .410 lift gives great outcome with strong midrange torque but good top end power also. Cost of replacement of valve train the barrier, but if serious do this and the needed porting to match.

This sort of cam is great for both road as well as track day and race applications. The last step is to replace this cam on a race engine with a .490 lift 320 seat to seat inlet cam while leaving the shorter duration cam on the exhaust, this gives more top end around 8000 to 9000 rpm while not loosing to much in mid range torque.

cheers
Rohan
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PostPost by: mark030358 » Thu Jun 09, 2011 12:08 pm

I agree with Rohan, QED 420's are really top cams. I've just fitted a pair :)

Mark
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