Lotus Elan

Trigger for a whole heap of work...

PostPost by: 2cams70 » Tue Jul 02, 2019 1:04 am

It is possible to purchase gaskets of different thicknesses to compensate for varying deck heights. See link:

https://www.lotusmarques.com/info/techn ... sket-guide

The best and cheapest bet is to buy your own gasket material (you then have the choice of the best quality material) and cut them yourself. It's relatively easy to do with an Exacto knife and some hollow punches. The best cork gasket material to use is the sandwich type. This has an aluminium foil reinforcement sandwiched between two thin layers of cork. The aluminium reinforcement helps stops the cork from extruding under pressure. The timing chest gasket that came in the kit I bought from QED was the cork sandwich type. A lot of them are fully cork without the reinforcement.

You can use some of this stuff too to help stop the gasket extruding:

https://www.henkel-adhesives.com/us/en/ ... alant.html

I must say it's really ballsy of you to pull a Lotus engine out by the side of the road!! Definitely some pictures there for the grandchildren if you have them. A good incentive to get the job done in a hurry no doubt. Be careful of the local council though. Mind you it's an excellent excuse for getting out of a parking fine. Ummm sir - but my car has no engine!!
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PostPost by: JJDraper » Sat Jul 06, 2019 5:48 pm

Short block has been taken to my engine man and after a good inspection of the bores, he is confident that they are still good, just glazed and no wear lip. If the pistons are in the same state, they can be re-used with new rings and a hone. Need to check the ring land clearances though. This bodes well for the crank, which may only need a polish and new shells. More news when the block is torn down and inspected in more detail.

He confirmed that the block has been decked at some point, meaning there was no step between the alloy water pump case and the block. No wonder the cork gasket just squished allowing oil to p*ss out. He intends to machine the pump case to give an appropriate step - no more oil leaks, hooray!

With regard to the water pump itself, we need to check what the arrangement is and may even re-use the ceramic washers if they are in good condition. Apparently this is a problem area with pattern parts not being up to the job..

On another note, the clutch is close to the limit, so another bullet dodged, re having to take the engine out. This has done around 45k miles, fitted by Mattys. I note the friction material, looked at edge on is wavey, but worn flat - seems odd.

The work keeps piling up, but should be within budget.

Jeremy
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Why is the friction material wavey?
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Not quite down to the rivets but sooo close
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PostPost by: rgh0 » Sun Jul 07, 2019 12:27 am

The disk between the friction faces has its sections slightly offset to give some spring compliance so that the clutch takes up more smoothly producing the wave pattern you see on the edge. Under the clamping pressure this flattens out.

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PostPost by: 2cams70 » Sun Jul 07, 2019 3:06 am

Be careful in just assuming you need to machine the front cover. Measure twice cut once. With these engines you can't just assume the deck and head faces have been machined perfectly horizontally and that the front of the block is perfectly at right angles with the deck face. My engine was exactly the same but when I did a trial build by plonking the head back on with a gasket and then torqueing it up I found that lo and behold the clearance for the cork gasket was in fact perfectly OK. I reckon it's always worth buying two cylinder head gaskets of the same type as you intend using. Accept the fact that you'll use one for the trial build only and the other for the final build.
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PostPost by: JJDraper » Tue Jul 09, 2019 4:47 pm

Thanks for the heads-up re the step between the timing chest and the block. Mine has no step at all - completely flat across the block & timing chest. The cork gasket was squished to smithereens (see earlier pics), so an appropriate reduction in the height of the timing chest would be useful to reduce oil leaks. I trust the advice I have received for this.

The workshop have had the opportunity to tear down the block and examine all components for wear. The news is good so far. Pistons and ring lands have next to no wear and even the rings show little wear. His advice is to re-use the pistons, pins and rings, with a bore hone. I was somewhat surprised by this advice, but he knows his stuff. Similar story with mains and big end shells. OK, but will be replaced. Crank is on +20thou and big ends at +30, but all bearing surfaces good to go again.

Negligible corrosion of the alloy covers and they came apart and away from the block easily. Must have been all the oil leaks.

All in all good news and extreme surprise at the low wear levels internally. He is used to seeing Twin Cams knackered at 10k miles and pigs to take apart, so this one has been the exception. :)

I will deal with the head, as I have experience of working with these and replace the sprockets and chain, as they show some pitting and are a little 'sharp'.

The secret, IMHO is good synthetic oil, with regular changes; appropriate grade for summer/winter and, possibly most importantly, letting the engine warm up properly before thrashing it.

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PostPost by: Donels » Wed Jul 10, 2019 7:41 am

I agree with the synthetic oil but I’ve been told it prevents a 'new' engine from bedding in, so start with mineral oil. Anyone any experience on this?

Ref. machining a step. Is this usual? Mine is completely flat and I’d assumed they all were?
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PostPost by: types26/36 » Wed Jul 10, 2019 9:45 am

Donels wrote:Ref. machining a step. Is this usual? Mine is completely flat and I’d assumed they all were?

There is usually only a small step and it is mentioned in the w/shop manual.
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PostPost by: 512BB » Wed Jul 10, 2019 10:26 am

Personally I don't think it makes any difference what oil is used in a Twin Cam engine wear wise, so long as it is suitable for same and is CHANGED REGULARLY. That is key.

Last year I rebuilt an engine from one of my cars that had covered 40k miles since its last rebuild. The only reason I rebuilt it was because it was leaking to much oil and I was fed up moping up! Over those 40k miles, I had shuved everything and anything into that motor, including oil that I inherited from a dear friend, that was at least 30 years old, but obviously new :roll: All the oil used in the engine over that period was mineral oil.

So, on rebuild, what was required? Just the journals had a light polish and new, same size as removed bearings. Bores were not touched, not even deglazed, as there was no discernable wear. Pistons and rings were just ultrasonicly cleaned, kept in exactly the same positions as removed, and replaced.

Change your engine oil frequently gentlemen, whatever you choose to use. You know it makes sense.

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PostPost by: 2cams70 » Wed Jul 10, 2019 10:56 am

types26/36 wrote:There is usually only a small step and it is mentioned in the w/shop manual.


They are talking about the steps between backplate and front cover and between backplate and cylinder block sump mounting face. They don't mention or include the step between the backplate and the cylinder block deck face which is the one which affects the cork gasket compression. If you do a trial build with cylinder head gasket in place and determine the actual clearance there and hence the amount of compression of the cork gasket you can't go wrong.
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PostPost by: JJDraper » Mon Aug 12, 2019 12:26 pm

A little update. The engine has been fully disassembled and inspected, with as close to no wear as a feeler gauge can discern. We therefore intend to change as few parts as needed - bearing shells, just because we are in there; all cam/crank sprockets and chain, gaskets and the fiercely expensive +5thou thrust washers.

I know the adage of "freshly rebuilt engine sir (with all the old parts)" , but having inspected the parts myself, I can understand why.

Judge for yourself from the pics, and bear in mind this engine has done well over 100k miles in my ownership. Bottom end was rebuilt (well) by the PO, apart from the lack of a step between the block and the water pump housing and had covered some mileage before I got it. The lack of the step was due to not positioning the cover correctly before tightening it, as was pointed out by Type26 - a common problem apparently. So no machining required.

I am staggered by the lack of wear on the pistons. Only No.4 shows the slightest wear at the base of the skirt. Everything else is almost as new.. ring gaps, lands etc. Bearing shells show very slight wear and the crank journals none. These parts have not been cleaned, apart from a wipe over with workshop tissue.

Change that oil regularly.

Jeremy
Attachments
p1040091.jpg and
p1040087.jpg and
p1040086.jpg and
p1040080.jpg and
Hone marks still clear
p1040090.jpg and
p1040096.jpg and
A pile of bits
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PostPost by: 2cams70 » Mon Aug 12, 2019 11:46 pm

JJDraper wrote:The lack of the step was due to not positioning the cover correctly before tightening it, as was pointed out by Type26 - a common problem apparently.


Best to use a centralisation tool on the crankshaft to align the front cover. It's easy to have one made up. If you overtighten the three bolts that screw into the top of the cover this can pull the cover out of alignment and toward the head. It really is a bad design. It really needs dowel pins to keep things in correct alignment during service.
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