Headgasket questions.
 

I have been looking for a mls gasket. I have found some. Was wondering; What is the rule for the bore diameter? Can you have a bigger bore diameter than what your block is? Most I have found are 78.5mm bore size. Really need some clarifying. Thank you all!

If you are asking if the bore diameter of the head gasket can be larger than the cylinder bore in the block, I would say it almost has to be larger, as there is some slop in the fitment of the HG on the block deck. We wouldn't want the inner edge of the HG fire ring to interfere with the piston protrusion over the top of the deck.

That's my common sense answer, sorry no exact numbers.

Hopefully someone else with more definitive answer will chime in.

Agree, plus maybe the gasket makers are also leaving some extra margin for engines with larger than stock bore size due to overbore during rebuilding. Stock bore size is 76.5mm and the second oversize goes out to 77.5mm. I don't think I have ever seen a special overbore headgasket so they probably manufacture them all to accommodate the largest possible bore diameter.

The 78.5mm size of the gasket would do that plus a little room for error with gasket positioning as you say to be sure it will clear the protruding pistons. So that 78.5mm size is probably appropriate.

Foghorn117 where have you been finding the MLS gaskets? Most of us here have had a hard time getting them for some years now. Shipping in from Europe or do you have a N America source?

I have found some on ebay. But you really have to look on the German eBay and translate it. You can also use the acl vw2.4d gasket.