Lotus Elan

SE or Sprint cams in an old engine?

PostPost by: Quart Meg Miles » Thu Mar 16, 2017 10:16 pm

Even with a 3.9 diff the close-ratio box, which I wouldn't be without, seems to make the car sluggish compared to others and with my engine stripped I thought I would upgrade for the first time. My advert for SE cams produced only an expensive offer of Sprint cams but there is a set of SEs on ebay UK at the moment. Could some more experienced member pass an opinion on their condition, from the photos, please, they don't look as good as the ?150 knock down a few months back:

http://www.ebay.co.uk/itm/282392544381?ul_noapp=true

Alternatively I could regrind my own, or preferably some other, cams to QED Sprint spec (for ?204) but my whole car is high mileage and might not like the torque. I have a SE exhaust to fit and would keep the transverse silencer and try leaving the Webers as standard (which is certainly OK for SEs) as I'm not going to drive the bells off it. Any observations on the outcome would be welcome, I'm trying to assess practical solutions to the low power syndrome. Do SE cams give any improvement at low-medium engine speeds?

I realise, from reading archives, that I need a new set of followers whichever route I take.
Meg

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PostPost by: Stevie-Heathie » Fri Mar 17, 2017 9:41 am

Hi QMM

I'm currently upgrading my 67 SE engine for the first time. I took advice from this forum a month or so ago - you will see my thread if you search.

My experience might of interest:

I got a baseline power run done on a rolling Road which told me my starting point (93bhp at the wheels so pretty bang on for an SE but a bit smokey). I want a bit more poke but n reliability impact - fast street use they call it.

Max500 in Guildford is doing the engine work. He found I had big valves and SE cams and we decided to:
1. machine new valve guides (to reduce the smoke!)
2. clean up the porting
3. Install qed 420 cams and the necessary springs if the piston cut outs are deep enough (360 if not)
4. Install vernier timing kit
5. Rejet carbs as necessary.

Work is ongoing at the moment.

Then I'll go back to the RR for a final tune and power run to compare before and after.

HTH

Steve
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PostPost by: HampshireMush » Fri Mar 17, 2017 10:22 am

Steve

Would be interested in your feedback abouit Max500. I have used Max before when he was at Lakeside but not sure about this new setup as Lakeside is still trading as well.

Is he on his own there and what are his turnaround times like?

Also interested in any other feedback on this as I am contemplating some engine work myself later in the year.

Thanks

John
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PostPost by: Stevie-Heathie » Fri Mar 17, 2017 11:08 am

Hi John

Yes, it's Max from Lakeside. I believe he did the "older stuff" there whilst his colleague would focus on the Elises, Exiges, etc. Was an amicable departure, he now is set up as MAX500 in nice shiny refurbished premises in Guildford 5 mins from his home, something he's been planning for years he told me. Can't really comment on how my engine will turn out until it's done, but I'm quietly confident.

Always a pleasure to deal with Max and he definitely knows Elans inside out.

Best
Steve
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PostPost by: Quart Meg Miles » Sun Mar 19, 2017 12:07 am

Stevie, I'm looking for a much smaller amount of work than you are committing to as I want the car back on the road.

It's interesting that you have big valves but SE cams. The valves wouldn't have been around when your car was made so has it had a head swap?

:idea: If I don't get the ebay cams on Wednesday I'll petition you for your discarded SE cams! Expect a PM.
Meg

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PostPost by: nigelrbfurness » Sun Mar 19, 2017 9:44 am

Meg
In my experience, S/E cams will not provide much of a noticeable power increase over standard cams - the low down torque feels less and you will have to rejet your carbs anyway. If you use the standard weber settings for S/E cams you will find that there is a flat spot low down, the usual fix is to go down one size on the chokes which reduces the maximum power slightly again. The S/E cams move the power band up the rev range a bit and that's not really what you want on a high-mileage engine - if that's what you meant by "old" :) as to enjoy the benefit you will have to be fairly heavy footed. An engine that is at the low end of the acceptable compression range will probably not benefit at all from a cam change from STD to S/E.

If your standard cams are worn then I suggest regrind them to the standard profile and reset the tappet clearances. Worth checking the wear on the cam followers too at the same time - wall and ceiling!

If you are overhauling the engine - crank grind, rebore etc, then go to Sprint cams or QED 420. It has been said many times before that going to big valves without a wilder (than sprint) cam will not give you much benefit and I agree with this, just makes it harder to get a good idle and low-down pick up. I think Miles Wilkins reckons on 2bhp as the difference between big valves and standard size valves.

Good luck with your mods! It is always useful to hear what the outcome is - all adds to the knowledge base.

Nigel F.
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PostPost by: Quart Meg Miles » Sun Mar 19, 2017 11:26 pm

Nigel,
Thanks for that summary. I had a S130/5 and that pulled like a train with extra lifts at 2500 and 5000 rpm despite the extra weight. It felt like a bigger engine. I thought SE cams might have taken me a little way there but perhaps it's all in the gearing. After all, they dropped the Sprint to a 3.7 diff from 3.55 as fitted to the Super SE to emphasise the acceleration.

Yes, old as in 275,000 miles but still the original crank (showing 0.001" wear) while cams still look good and used to be run regularly to 6,500; the secret of long life is to warm the engine thoroughly and I fitted an oil temp gauge. Re-sleeve was ten years/33,000 miles ago and you've probably seen my recent thread on head bolts.

I think perhaps I'll rebuild as standard and then check the compression, which I haven't done recently. If that is good then changing the cams is not a big deal and I can always change back. I had hoped someone might respond about Sprint cams with virtually everything else standard but perhaps that's too much of a mis-match and the extra torque might damage the (old) drive train.
Meg

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PostPost by: Quart Meg Miles » Mon Mar 20, 2017 11:11 pm

Today I measured the lift of my camshafts which don't look worn in any way. (I had a 205 GTi with hot cam which wore flat faces onto both sides of the lobe peaks). The base radius of the cams were all 1.205" and all the inlet lifts were 0.345" and all the exhaust lifts 0.343". Wilkins book and a posting I found from 2004 quote 0.375"; can I really have lost 0.030" off all the cam lobes with such precision? All except one followers are the originals.

Alternatively is the 0.375" a misprint for 0.345"? It seems odd that the standard cam should have a greater lift than the higher tuned ones, especially as one posting stated that the twin cam engine was more responsive to lift than to dwell. :?
Meg

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PostPost by: nmauduit » Tue Mar 21, 2017 9:07 am

Quart Meg Miles wrote:Alternatively is the 0.375" a misprint for 0.345"?

Regarding camshafts my 1989 copy of Miles Wilkins' book indicates p180:
B-type (standard) no groove 0.375 total lift
C-type (S/E) one groove 0.3498 total lift
D-type (super S/E, Sprint) two groove 0.36 total lift
E-type plain 0.3659 total lift
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PostPost by: rgh0 » Tue Mar 21, 2017 10:45 am

Wilkins is wrong (sorry to say such a Blasphemy)

IMHO
std and SE cam .350 lift
sprint cams .360 lift

Lift is above base circle not valve lift and actual cams may vary slightly depending on wear and grinding tolerances

The confusion comes from the FIA paper work submitted by Lotus for the 26R where the coil bind lift of .375 was confused with actual cam lift above base circle of .350. Probably may be a deliberate error if it allowed Lotus to run a higher lift cam ???

But it shows that the Saint did not measure up everything himself that he quote in his book :lol:

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PostPost by: Quart Meg Miles » Tue Mar 21, 2017 11:04 am

rgh0 wrote:Wilkins is wrong (sorry to say such a Blasphemy)

IMHO
std and SE cam .350 lift
sprint cams .360 lift

The confusion comes from the FIA paper work submitted by Lotus for the 26R where the coil bind lift of .375 was confused with actual cam lift above base circle of .350. Probably may be a deliberate error if it allowed Lotus to run a higher lift cam ??? :shock:

cheers
Rohan

Thanks Rohan, that makes sense and puts my cams in the camp.

Then there are all the ignition profiles which beggar belief.
Meg

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PostPost by: rgh0 » Tue Mar 21, 2017 11:13 am

Yes I just try to ignore the ignition profiles as many of them make no sense due to confusion over the data. In the end for a Weber engine you need around 25 to 32 degrees total advance that comes in around 3000 to 4000 rpm depending on the engine build and fuel you use. Build it and then dyno it to get the advance curve you need. So much has changed since the original curves and some many errors crept in that its not worth trying to decipher them --- believe me I have tried.

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PostPost by: nmauduit » Tue Mar 21, 2017 4:52 pm

rgh0 wrote:Wilkins is wrong (sorry to say such a Blasphemy)
IMHO
std and SE cam .350 lift
sprint cams .360 lift


so the "B" profile would be described wrong in that book - but as for swapping a measured 0.35 cams for "S/E" cams it would be correct ("C" one groove), confirming for the case at hand there would not be any lift to be gained by a swap for S/E.

To gain lift Sprint cams would be a first step (CPL2 is supposed to be rather close to that, and Q360 is presented as a "modern equivalent").

I would not think that this change alone would feel drastically different (unless the engine was significantly out of tune), but on the other hand a lower power (by construction or otherwise) probably helps to make the car last longer. The Q420 route mentioned above could be more palatable, but the trade-off is a bit more bold (and costly : a set of Q55 springs and retainers, which may not be a bad idea if the original ones have covered a high mileage)...
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PostPost by: Orsom Weels » Tue Mar 21, 2017 6:32 pm

OK guys, What have I got then ? I have an early twincam, LP3489 LBA, four bolt crank, mk 1 head, all std valve sizes, un-skimmed & correct compression ratio, std Lotus spec'd 40 DCOE's & correct spec dizzy for std engine. The cam's have no groove or identifying marks, they give std cam valve timing & have a lift of .374/5. Given the info in MW's book, I had always assumed they were just Lotus std cams. :?
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PostPost by: rgh0 » Tue Mar 21, 2017 7:38 pm

Orsom Weels wrote:OK guys, What have I got then ? I have an early twincam, LP3489 LBA, four bolt crank, mk 1 head, all std valve sizes, un-skimmed & correct compression ratio, std Lotus spec'd 40 DCOE's & correct spec dizzy for std engine. The cam's have no groove or identifying marks, they give std cam valve timing & have a lift of .374/5. Given the info in MW's book, I had always assumed they were just Lotus std cams. :?



Do you know what base circle the cams have. That will tell you if they have probably been reground at some stage to a non original lift. 0.375 could never have been a standard production lift as you are just to close to valve spring bind

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