Thankyou, thankyou. I understand the "Dizzy" thing. I also understand that the steam vents exist between the siamese cylinders, but are separated. A steam vent exists on the intake side of joining of cylinders and on the exhaust side because water can not flow between them. BUT, did chevy make 400 blocks without the steam vents. I have a block without them, would you guys recommend drilling them in the block as well as the 350 heads which I will use, as marked by the 400 head gasket.

bobvette62