Join Date: Feb 2002
Location: N.W. Washington
steam holes in 400 heads are not necessary in a even slightly performance oriented motor. if you have moderate gears or any stall on an automatic, the holes usefulness is nada, since the rpms are always slightly up. the reason gm did it was so that the trucks and vans and taxicabs the 400s came in could sit and idle all day with no heating up issues. they are purely a low rpm deal.
myself and all my buddys with 400s (4 or 5 of them) don't run steam holes, and have no problems. i regularly cruise my car around, idle it, etc, and it cools just fine, even with a factory copper/brass radiator.
so unless its going to be an all day idler, id skip the steam holes, its just another place for cracks to form, imo.
1968 rs with an old school 354" SB2.2 pump gas motor.
Repetition does not transform a lie into a truth.
Franklin D. Roosevelt