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TOP end engine noise on recon engine


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I have just read a post on engine knock in a recon engine on the Moss wed site. Where the pistons were hitting the head because the block had been skimmed.
I have just rebuilt my Spitfire 1500 engine. I bought a recon short engine re-bored +40 and unleaded recon head. I have changed everything except the camshaft and push rods.
When cold it runs very nice but when it gets warm there's a top end noise that’s there all the time. I have adjusted the tappets many times and checked the cam followers were not sticking. I have now taking off the head and checked cam followers and pushrods and all looks ok.
The engine and head were advertised as both being lightly skimmed. The pistons look dead flush with the top of the block although I have not measured with a straight edge and feeler gauges yet. So I'm wondering if this is the same problem.
Are all Spitfire head gaskets the same thickness and what about cylinders that have been bored out to +40, is it ok to use a standard head gasket because the fire ring on the gasket come into contact with the piston head when hot.
I have also just bought a new cam with new pushrods and followers. But have this feeling that replacing these and putting it back together I will still get the knocking.
Any advice would be greatly appreciated.

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Further to my comments above..I have measured with a straight edge and feeler gauge and there's 10thou clearence between block surface and piston crown which I believe is OK. But I have had a good look at the head gasket and it seems that has been flattened by the piston on bores 1 & 3 where the bores 1&2 + 3&4 meet.
I think that because the cylinders have been bored out too +40 the head gasket overhangs the bored. Not sure where to go now, maybe reduce the piston heads around the edges to give them a very slight dome.
Any thoughts on this......other 1500 triumph owners must have had the same problem I would have thought when having the block bored +40. not sure if this is the maximum rebore allowed.

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Dan, not had a spitty engine, but the  6 is the same, and im on 60 tho ob, and no probs,

are you sure threr is clearance on pistons that are ..catching..

if they are catching, it may well be that the head has compressed the gasket doon,

if it is compressed doon, by how much has the pistons compressed it,!!!!

if its only a few thou, it should be ok, as the gasket is fairly thick, so a few thou compression wont really harm it,

but if it has compressed it, that it cant compress it any further, then this is  no good at all

Are ye sure that the ..correct.. gasket has been fitted!!!,

have a loook ,and report back, thats a good chappie

regards Marcus

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On the 1500 there should be a 45 degree chamfer on the top edge of the piston,on non genuine pistons this machining is frequently too small or missing completely, causing the problems you have there are two ways to cure it,  get some ae pistons, which are coorectly machined  or have the ones you have machined to the correct chamfer, it was 3 years ago i had this problem from memory the chamfer should be 1.5mm and 45 degrees
It occurs mostly on +030 or larger bores and only with recessed head gaskets
whatever you do dont put it back together like this as it will destroy head gaskets

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