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Stripped head off again today, the composite gasket used looks like it has disintegrated all the way along the top edge of the cylinders, the black Viton coating has disappeared leaving the metallic inner showing through, parts of it look like they’ve been on fire! Never seen anything like it before on any engine. Not sure how to resize pix or would’ve posted some, I’m totally aghast!

Jasonking wrote: ↑Thu Jul 25, 2024 11:00 pm Not sure how to resize pix or would’ve posted some, I’m totally aghast!

If you email me your pics I will resize and send back to you for posting. Have sent you a message with my email address.

Jasonking wrote: ↑Thu Jul 25, 2024 11:00 pm Stripped head off again today, the composite gasket used looks like it has disintegrated all the way along the top edge of the cylinders, the black Viton coating has disappeared leaving the metallic inner showing through, parts of it look like they’ve been on fire! Never seen anything like it before on any engine. Not sure how to resize pix or would’ve posted some, I’m totally aghast!

Earlier in thread you had good compression, how did you know ?

EDIT: I am not trying to catch you out BTW, my concern is that if you dont carry things out in a reasonably ordered and logical way, you may be creating extra work and expense for yourself........and if you do pass to a mechanic down the line, they may charge you for undoing whats been done

https://mk1-forum.net/viewtopic.php?p=342895#p342895

As I mentioned before, the problem it wouldn't run is the compression figures you mentioned.

The highest 105 psi is low but the 50 and 70 odd figures are simply too low for the engine to fire and run.

You seem to have discovered the culprit, the head gasket. Why it failed is another question. I'm wondering why you had the head skimmed in the first place. Have you checked the block face to see if it is OK ? Have the valves been lapped in correctly (although doubt it would cause head gasket failure but would explain very poor compression )

There's various views on head gaskets but we have always used Payen copper/asbestos head gaskets and have never had a problem, old stock ones (providing they're in good useable condition of course) are perfectly OK for a standard-ish engine. Not saying composite aren't any good just our own personal preference. Correct torquing in the correct sequence is very important.

hi mate
you probably need the block decked to make sure that it is true if it is out the head will not seal properly also may be use a different head to see if that
makes a difference the block only needs to be a few thou out in the middle and you have that head gasket problem
mini heads being cast iron they do not seal as good as alloy ones so every thing has to be spot on for best results when i rebuilt my laser engine i had the head checked [ alloy] failed to soft newer head ok block decked and rebored retorque head gasket and all was well for 200k then water pump failed back to square 1
good luck cheers roger mcnab

Some photos

Photo

I'd say something has been trapped or fouling when you've torqued the head down, meaning that whole back edge hasn't been tight.
I don't think thats a head gasket problem, but an install one.

Have you undone the rockers at any point since it was assembled ?
That looks like it's had a hydraulic lock when torqued down.

A bit off topic, many years ago I bought a couple of that type gasket. After using them on 998s I order some more only to find them NLA from MSC. Are they still available down under? Steve (CTR)

Sorry for my earlier reply i must have missed the postings on poor compression readings

Beyond all the great advice given by all the other replies…. I would replace the old head studs. Preferably something like ARP.
I solved my head gasket failures with them.

timmy201 wrote: ↑Fri Jul 26, 2024 11:01 amPhoto

Why is the cylinder holes ovalled?

floormanager wrote: ↑Fri Jul 26, 2024 7:08 pm

timmy201 wrote: ↑Fri Jul 26, 2024 11:01 amPhoto

Why is the cylinder holes ovalled?

Most (all?) small bore head gaskets are like that

That hasn't been torqued down properly I'm afraid.

timmy201 wrote: ↑Fri Jul 26, 2024 9:52 pm

floormanager wrote: ↑Fri Jul 26, 2024 7:08 pm

timmy201 wrote: ↑Fri Jul 26, 2024 11:01 amPhoto

Why is the cylinder holes ovalled?

Most (all?) small bore head gaskets are like that

Thanks, I'm only recently (in the last 40 years) seen large bore.

CooperTune wrote: ↑Fri Jul 26, 2024 1:23 pm A bit off topic, many years ago I bought a couple of that type gasket. After using them on 998s I order some more only to find them NLA from MSC. Are they still available down under? Steve (CTR)

I don't know if its the same, but it looks like the Victor Reinz small bore gasket, which seems to be widely available.
https://www.minispares.com/product/Clas ... o%20search

Tim

timmy201 wrote: ↑Fri Jul 26, 2024 9:52 pm

floormanager wrote: ↑Fri Jul 26, 2024 7:08 pm

timmy201 wrote: ↑Fri Jul 26, 2024 11:01 amPhoto

Why is the cylinder holes ovalled?

Most (all?) small bore head gaskets are like that

Useful when a small bore block is 'pocketed' to clear the exhaust valves
eg. when fitting a 1275 cylinder head.

does anyone do a round one to match the bores ?

In my relatively short time working on minis I haven’t seen a round hole small bore gasket