Lotus Elan

Cams and timing query..

PostPost by: Sploder90 » Tue Jul 02, 2019 1:40 pm

Hi all

Apologies in advance for the length of this post..

My initial investigation into a leaky water pump now has me wondering what else may be uncovered as I pull things down...

Thought it would be a good idea to set cam timing before commencing the pull down of the head / front cover etc.

At this stage the lump is still in the car. This may change!

After getting it to TDC I looked at the cam marks and they were a bit out.
Exhaust when aligned horizontal required the timing to be around the 10° BTDC mark. The inlet mark was not pointing at the exhaust mark..
Thinking the mark on the pulley may also be slightly out I got out the dial gauge to double check and with a little bit of allowance for the dwell at TDC the pulley mark is pretty much spot on.
At least I have a base line, start to strip the head. Happy days...

Head is now off & I am kicking myself (to save you guys the trouble) as I really really should know better after all these years, that I did not take more measurements including getting a crank angle gauge and measuring the valve MOP.
Score 0 for patience.. Dohh!!! :oops:
Hell, I didn't even do the compression but that takes a bit of doing without a starter motor... another story..

Now, the curious thing is that one cam has a machined groove indicating a C type cam and one has no groove indicating a B type ??

Message to self, should have Noticed this rather obvious difference and put the sprockets back on & measured the valve opening with the dial gauge....before whipping the head off!
More self flagellation!

Quick and dirty check with cams in head indicates possible different lift... Though granted it was getting late & this is not exactly a scientific method!!
Have not measured the lobes or base circle as yet as now away from the car for a while but a point to point with a digital caliper when I noticed the oddity indicated 0.8 'taller' inlet cam. 36.46 mm V 35.68 base to tip.

This then had me looking at the cars previous history and there is an itemized bill from 20 or so years ago indicating head reworked and 2 x CPL2 cams.
I have some doubts on these as it was a non specialist garage only bill and the price was £40 each... Nothing in the file from supplier to substantiate this or where the cams came from.
£40 seems cheap even 20 years ago but I guess they may have been reprofiled? If so is there anyway if identifying who by and what they did?

Has anyone come across this before? 2 x potentially different cams / profiles on a road car?
Could it be deliberate and not just a PO bodge?
Was it just what a can reproduce had available in an exchange basis hence the difference with the grooves?

Have done a lot of searching on here, the wider net and Mr Wilkins book and so far drawn a blank.

Odd thing is when I first got it home, after it had pretty much stood for 10 years, following an oil and filters service even with a knackered distributor (rotor arm was machining the cap away..) and over fuelling / spitting carbs it was pulling pretty well..
Although with hindsight it did seem to take an awful long time to fill with fresh oil.. :roll:
Park it up for a couple of months for other work (rear A arms etc) and the water pump leaks... :?
Those seals don't like to be sat idle do they?


Currently reviewing possible options as have been finding a few other issues including a spurious looking bolt in the front of the timing cover, yet to be investigated.

The original plan was a rolling resto and try and use it this summer for more attention over the winter.
Now not sure as to the best course of action.

Not had chance to look in detail at the rest of the head or the bores for condition other than it looked a bit grungy especially number 4 but I was kind of expecting that next to the breather location in the air box. Really wish I had done the compressions when I serviced it...

Head bolts came out reasonably until trying to get them fully loose.. Looks like they may have been in / off and possibly over done as the washers have bitten the head in places.

next find was a considerable amount of very old and smelly oil in each head bolt hole
Bolt threads came out really covered in it and really carbonned up.
It absolutely stinks & has me a little concerned as the previously drained oil other than having a slight whiff of fuel (hardly surprising given the above) seemed quite clean.
The memory of how long it took to refill it makes me wonder if the oil ways / drains are clear?

Now, the big question:

Do I bite the bullet, pull the block out and do a full rebuild or do I get and just do a top end refresh, new pump and gaskets and try and 're time the possibly spurious cams?

Any advice, spare parts, beer vouchers, full engine for free or a pittance or the loan of a car for the summer welcome :)

Regards

Mel.

S3 SE: getting less complete and more expensive by the day..
But still smiling ... For now.
Last edited by Sploder90 on Tue Jul 02, 2019 2:40 pm, edited 1 time in total.
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PostPost by: JonB » Tue Jul 02, 2019 2:19 pm

If I were you I'd pull it, if only to inspect and have better access. You may not need a bottom end rebuild but it's best to know, wouldn't you say? That way you can build up some trust in the engine.

Despite what you uncovered, I still say you got a bargain. Even if you'd bought a more expensive car you'd have had no guarantee it was any better.

From your description I would think that a Summer of fun isn't on the cards... but just think about next Summer!
Late 1972 Elan Plus 2S 130/5 - UK - Unit 50/1115L
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PostPost by: JohnCh » Tue Jul 02, 2019 2:36 pm

Sploder90 wrote:Has anyone come across this before? 2 x different cams / profiles on a road car?
Could it be deliberate and not just a PO bodge?


20 years ago when I was building the engine in my Alfa GTV, an asymmetric cam setup was an accepted method to maximize power under the curve for those engines. That doesn't mean it is effective for the Lotus, or that it wasn't a bodge, but it certainly could have been deliberate.

-John
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PostPost by: Sploder90 » Tue Jul 02, 2019 2:45 pm

Cheers both.

Budget now set to include an engine hoist...and stand.

Might a easier doing the pump if not bent double anyway...
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PostPost by: JonB » Tue Jul 02, 2019 3:02 pm

You can do the pump in situ... apparently.. but it's way easier on a stand. Good call.
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PostPost by: Sploder90 » Tue Jul 02, 2019 3:21 pm

Looks like a trip to machine mart for a new stand on the way home this week...
Reverse car up and deposit new goodies in the garage...

The better half & even the postie have started to notice the stuff that is being delivered :lol:
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PostPost by: nmauduit » Tue Jul 02, 2019 6:00 pm

as an opinion on part of the issues raised only: CPL2 camshafts would be Sprint aftermarket equivalent at the time or just about, reground for £40 would be half today's price so that does not sound completely off to me. As for the base circle, it is also possible that the grinding process comes to 2 different base circles for the exact same 2 profiles, that could result from a number of things including initial camshaft condition. As for the sprocket alignment, this is an indication only and can only be relied upon on a stock engine: for reprofiled camshafts, timing the actual cams (rather than the sprockets) using a gauge on the followers (buckets) would have my preference (one may then make sure of proper timing and relative position of the sprockets for future reference).

If the engine was running just fine at some point before long storage, I would first try to get back to that point before deciding what to do.
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PostPost by: Matt Elan » Tue Jul 02, 2019 7:24 pm

It is a fairly common practice to have different cams - in my current long term rebuild I have a sprint (two ring) cam on the inlet and an se (one ring) on the exhaust. The engines not run yet but should be interesting when it does.......
I expect the engine to be a bit more powerful than a se spec unit but with a bit more tractability than a sprint. Time will tell......
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PostPost by: Sploder90 » Tue Jul 02, 2019 8:57 pm

Posts so far have me feeling a bit more confident in what I have. After 51 years and several custodians things are not going to be routine.
Have now found the spec of CPL2 on Burtons site.
Don't know if mine are from here originally but should hopefully be able to verify what I have when I get home.
Indication is a .350" lift so a bit of simple maths should tell me one way or the other .

Thanks all for the info this far.

Will keep you in the loop as to progress or regress...
Still going to buy an engine stand though :wink:

Mel
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PostPost by: rgh0 » Wed Jul 03, 2019 11:15 am

Different cams with shorter timing and perhaps also lower lift on the exhaust side are not unusual in Elan competition engines due to the different breathing characteristics of the exhaust and inlet ports when being pushed to their limits. This is little / no need in a road engine due to the shorter cam duration used on both inlets and exhaust so for simplicity sake they were made the same by Lotus

Why you ended up with what you have is you may never know as it could have been deliberate ( and misguided) or just some cheap rebuild to maybe fix a bad cam or maybe a mistake in doing only one cam. Or maybe the cams are actually identical an one started as a standard cam and one as an SE cam and both have been reground to the same profile but on different base circles due to the different starting points you would need to get them checked by a cam grinder with the right test equipment to determine their actual detailed profile.

If building a road engine to standard specifications I would not mess around with cams that clearly have a strange history and just fit two new sprint profile cams ( unless I wanted to spend the time to fully analyse the cams and their profile to see if I could get them back to where they should be) . If looking for more power than the Sprint cams can provide i would get some of the sort duration high profile cams and the valves and spring packs etc to suit.

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PostPost by: Craven » Wed Jul 03, 2019 12:24 pm

If cams have been reground with a different base circle then this would show up in wide 0.032” difference in shim sizes. All other things being equal.
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PostPost by: rgh0 » Wed Jul 03, 2019 1:07 pm

Craven wrote:If cams have been reground with a different base circle then this would show up in wide 0.032” difference in shim sizes. All other things being equal.


All other things being equal is the key comment and hard to determine without a lot of other detailed measurement of valves and seat location and other components such as follower thickness to confirm all other things are equal. I routinely do all these measurements when building an engine to ensure all other things are equal :lol:

The easiest way to determine cam base circle diameter is to measure the cam lobe width at 90 degrees to the cam lobe peak. This will be the base circle diameter in all cams except extreme extreme racing cams with a greater than around 330 crank degree seat to seat duration which no one except someone running an old style open wheel racing car cam would potentially have. These old style cams did not really work until around 6000 rpm so required precise gearbox ratio match to the exact circuit to hold the engine in the required 6000 rpm to 9000 rpm rev range during a racing lap

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PostPost by: Sploder90 » Wed Jul 03, 2019 8:06 pm

Thanks Craven & Rohan for the comprehensive replies and info. Invaluable resource this site with the knowledge and experience available.
Should be back home tomorrow & if time allows and I can escape to the garage for a couple of hours the plan is to lift the cams and take a close look.
Dig out the micrometer & the reading specs / magnifying glass.. (Think it may be time to go digital...)
In theory measure the base circle and subtract this from the base to lobe should tell me the lift..???
Can then compare this against the .350" for a CPL2 and see if anywhere near.

Will also give me a chance to look at the bearings and journal condition and hopefully I can make an informed choice (guess :)) from there.
Worst case 2 new or reprofiled cams

Just been kicking myself for diving in without checking the valve opening....probably have given myself more cause for concern than was really necessary... Time will tell.

Think I have come to the conclusion after 2 days of hotel food and someone else buying the beer that it is better the devil you know so looks like the credit card will be taking a run out...and the lump will be getting pulled / checked And reconned as necessary.
looks like the garage will have a new ornament in the shape of a twink for a bit...
Doubt I can get it in the house... Don't think I will ever be forgiven for using the last dishwasher for things other than dishes..

PS: Rohan. Loving the art work, have the same Corgi but lagging behind in the rest..

Cheers

Mel
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PostPost by: rgh0 » Wed Jul 03, 2019 8:24 pm

Sploder90 wrote:In theory measure the base circle and subtract this from the base to lobe should tell me the lift..???
Can then compare this against the .350" for a CPL2 and see if anywhere near.


Mel

Yes that is how to check the cam lift.

cheers
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PostPost by: Sploder90 » Tue Jul 30, 2019 11:42 pm

So after a bit of a gap with being able to get back in the garage I finally got chance to have a closer look at the head and associated gubbins over the weekend and found a bit of an unusual issue...

Now, not sure if this is some weird wear or a deliberate modification or a hang over from a prior issue but the rear exhaust side bottom cam bearing looks decidedly odd and first impression is that it has had an attack of the grinder...

As can be seen there is part missing but there is nothing obvious from any other components to indicate there is something fouling.

Option is a PO may have done this to allow tappet removal but not sure why...

As anyone else come across this before or even done this... and / or can anyone offer an explanation?

Intention was to change out the cam bearings anyway as showing signs of wear & already have a set on order with a while bunch of other stuff to rebuild the lump.

Measurement of the cams and Looking at previous bills indicates a regrind to sprint spec some time ago. No sign of cam bearings in the previous history so presume they might not have been changed at the time...

There are a few light scores in the cam journals which I am hoping will not be an issue.. Think that it might not have been too clean when it went back together, but the lobes look ok, unless of course anyone has a pair of decent cams looking for a good home :D

a bit perplexed by the state of the shell....

thumbnail-11.jpeg and


Cheers

Mel
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