Head Gasket Failure?

[Tom Brearley]

Chris - thanks for the moral support. I'm coming round to your way of thinking. My main worry is that something more complicated is going on; I will do the work; and it still won't run properly. Hence my question in the subject of this thread.

Vic - thank you for the tip.

[Not_Anumber]

Be optimistic and assume it is the head gasket rather than anything bottom end related.
Everything points to the former as there is no other mechanical failure that would substantially reduce the compression on 2 adjacent cylinders to exactly the same level as each other.
A garage would start with taking the head off, do the job and then recheck compression. They should only need to go further if there was no evidence of gasket failure and the compression was still bad on those 2 cylinders on reassembly.

By doing it yourself you can guard against an unscrupulous unknown garage taking your wallet for a long drive for an unnecessary full engine rebuild.

[Tom Brearley]

Well, I got the head off yesterday and the diagnosis was correct. The head gasket had blown through between cylinders 3 and 4.

Twice! Bit surprised to find two gaskets in situ: a metal one on top, and a Payen type beneath. Is this normal? It's an Ivor Searle rebuilt engine which I bought 15 years ago. Ought I to use two gaskets when re-assembling it? Seems odd.

(I've asked this question in Another Place but would be glad of more views.)

[Vic Butler]

The bottom gasket in the picture is the same crummy gasket as I had. The MGB Hive sell a gasket kit with a Payen gasket and that's what I'll be buying. Don't use 2 gaskets.
Very odd using 2 different gaskets. Go with a Payen. Has the head been off the engine since you bought it? If not, it's a strange combination for a rebuilt engine.I'd get the cylinder head checked for warping like I've done.

[Vic Butler]

I've been looking at Payen gaskets on line and looking at the MGB Hive site, the bottom black, red and gold gasket in your photo is a Payen. I have an unused gasket set with that gasket and it says Payen in small writing on the packet. Perhaps I was unjustified in calling it a crummy gasket and it's down to my crummy torque wrench which will be replaced with a torque adapter.
I reckon 2 gaskets were fitted to cover up a fault in your case.

[Not_Anumber]

Im wondering if the engine builder used 2 gaskets to reduce the compression ratio slightly or perhaps to provide greater valve clearance. It may be worth looking into.
Very strange that someone would use 2 gaskets otherwise unless they were trying to accommodate a slightly warped head etc

[Vic Butler]

Surely no reputable engine rebuilder would use 2 gaskets. It sounds like a Mickey Mouse business to me.
If the head was warped it should have been checked and rectified if necessary.
It would be advisable to get the head checked.