Can someone explain this dimension to me? From what I gather head gaskets for a standard bore 350 use a 4.125 bore size for the head gasket.

But I measured the 40+ year old head gaskets I took off the heads and they measure 4.065. So, to me that is pretty tight considering the bore is 4.057. At any rate, is 4.125 the new standard? Would I benefit from a smaller bore diameter? I believe cometic can custom make them what ever size you want.

When the gasket bore size changes does that affect fitment as it relates to the coolant passages, etc.?

I was all set to buy a set of head gaskets, but want to make sure I get the dimensions right.

Thanks
d1