Lotus Elan

Head gasket reuse

PostPost by: pptom » Thu Dec 19, 2019 11:34 am

Hopefully an easy question, building my engine up again and i want to check the valve / piston clearance. QED advised and sold me a copper head gasket.
If i use this in the initial measurement build, will it be ok to use again on the final build?
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PostPost by: vxah » Thu Dec 19, 2019 1:15 pm

NO! Why not use the old gasket for the measure up? Save your cash, remember it's a Lotus your working on, never bin anything you take off...Least for a while!
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PostPost by: pptom » Thu Dec 19, 2019 1:23 pm

Old one was composite, think its gone to landfill.
I've got boxes of old worn out bearings and other parts removed from various projects which will never be used again, guess i have to up my game even more!
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PostPost by: nmauduit » Thu Dec 19, 2019 3:34 pm

I would go by QED's recommendation.

If that entails a dry fit with the copper gasket, just don't torque it up and account for that in the resulting clearance (hopefully this should be negligible, as a copper gasket would not be the first choice in a full out race engine requiring accurate minimal clearance)
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PostPost by: pptom » Thu Dec 19, 2019 5:08 pm

Thanks, gone with some q420 cams and i also have omega std pistons going in, so just want to make sure there are no clearance issues.
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PostPost by: 2cams70 » Thu Dec 19, 2019 11:22 pm

If you want to do the job properly buy two new gaskets the same as you are going to use. Reserve one for the trial assembly only and use the other for final assembly. They aren't that expensive. It's not worth the risk of reusing an already compressed gasket.

During the trial assembly measure the cylinder volumes to calculate compression ratio, check valve to piston clearances and also the front cover to cylinder head clearance for correct compression of the cork gasket that is installed there.

Having said that I've already been through the process with the same mix of parts as yours and can confirm that there's heaps of clearance valves to piston. The standard Omega pistons have deeper valve pockets than original.
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PostPost by: pptom » Fri Dec 20, 2019 6:23 am

Thanks, think i'm going to do the trial fit with the copper gasket and buy a composite for the final build.
The composite is slightly thicker, and 1.5mm wider bores and more expensive, but i feel a bit more confident using that. I had one on the last build with no leakage issues.
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PostPost by: 2cams70 » Fri Dec 20, 2019 8:12 am

For the trial build you should use exactly the same gasket as you use for the final build so you can be sure the gasket crush and thickness when the head is torqued is exactly the same as the final build. Nothing wrong with a copper gasket. I just went for a composite for mine because I needed one thicker than standard because of excessive head skim and with larger bore holes because of the overbore size. 44 degrees C at the moment here in Melbourne by the way!
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PostPost by: rgh0 » Fri Dec 20, 2019 8:19 am

The copper gaskets compress around 25% under design torque loads. The composite fibre gaskets compress around 30% so if its gives OK clearances with the thinner copper gasket ( typically 1.2 mm uncompressed) they will be about the same with the slightly thicker composite fibre gaskets ( typically 1.5 mm uncompressed)

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