Which Gasket?

[mrg21201]

My 416 blew a head gasket and the only two sizes i can find are 86mm and 89mm. Anybody know which size i need for sure. Thanks

[02440exkid]

I'm in the same predicament someone told me that I can used 85mm and it will hang over the sleeve a lil but the piston does not come all the way up and they said it will seal fine so I'm putting motor together tomorrow and I'll see how it works. I'll let you know if their any problems. ;)

[F-16Guy]

The 86mm will work fine. It's only 1mm smaller in diameter, so thats really only 1/2 mm overhang around the cirumference of the bore. You can also run the 89mm with no problems (that's what I have now).

[02440exkid]

is the 85mm ok too?:ermm:

[F-16Guy]

Yeah, that's kind of what I meant. The stock size gasket will work with a 406 and a 416, but anything bigger, and I would go up to the 89mm. If you blew a head gasket, chances are you will need heavy duty head studs. These engines are notorious for pulling head studs. When the aluminum cylinder gets too hot (especially up front around the forward stud because of the exhaust ports), the aluminum breaks down and weakens, allowing one or more of the studs to pull and stretch the threads. Companies like GT Thunder will install larger diameter studs and tap the new threads with a roll-form tap, which creates threads by compressing the aluminum in the holes instead of cutting it away. That makes the new threads more dense and much stronger. It's money well spent for a high compression 400ex.