Speedmaster Small block porting tips and results Part 1

The more common gaskets have a way bigger bore than most blocks can even be bored to.
So, if you go out to that size, the chamber will be out past the bore of the block.
I was just curious what he used.

He may have had something like a used 4.040 Cometic gasket hanging on the wall.

The Fel Pro 1008 is 4.160