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I was shopping for head gaskets today (1971 402, .030" over = 4.155) and am even more confused now. There are just to many choices out there. I swear the guy at the machine shop said something about "tin" gaskets I guess he was referring to a steel core laminate? Should I try to find one with the 4.155 bore, or is a stock 402 gasket ok?

Is there more of a chance for problems if using a thinner gasket? Pretty much stock 049 heads, other than new valves to match my Lunati cam (60203) and KB domed pistons (smiler to stock)

Can anyone recommend a good head gasket for this application, and also, how would I determine the approx. CR this engine will have?
 

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You will have 8.5:1 CR if you are lucky and your 049s chamber volume is close to 113cc.
Less if it is closer to 119cc...... Can't tell til you measure the chambers and without a piston number/dome volume......it is all a scientific wild-ash guess.

edit,
You'll find most of the BBC head gaskets have the bore quite a bit larger than your cylinder bore.
Look online at the catalogs...something common like Fel Pro head gasket for 402....it should list the bore.
Fel Pro knows a lot more than me about sealing heads to the block
 

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The bore size of the gasket should be slightly (.030" to .060") larger than your cylinder bore size. There is a chamfer at the top of the cylinder that must be taken into consideration. If the gasket bore is smaller than the cylinder bore, the gasket will get hot an will possibly cause pre-ignition.
Pre-ignition leads to broken pistons and all kinds of other nasty stuff.
 

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I swear the guy at the machine shop said something about "tin" gaskets
Too many people can't figure out the difference between sheet steel or sheet aluminum and "tin".

For example, Reynolds Wrap is "Tin foil".

Selling a long block with valve covers, timing cover, oil pan gets advertised as "Engine--with tin".

If he's talking about "tin" headgaskets, he probably means the stamped-sheet-steel "shim" gaskets such as Mr Gasket # 1131.

http://store.summitracing.com/partdetail.asp?part=MRG-1131&autoview=sku

They are a Godsend for engines that have the pistons ~.020 in the hole. They're very inexpensive at $20/pair. You'll have to have FLAT and SMOOTH gasket surfaces for them to seal, and unlike the discontinued GM steel shim gaskets, these won't support parallel-flow cooling on those few MK IV blocks that have the parallel-flow cooling holes in the block decks.

They need sealer on both sides before installation. "Aluminum" spray paint, CopperCoat, Indian Head, High Tack...hell I think mucus would work. Last time I used 'em I painted 'em with plumber's teflon thread sealer.
 
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