I have a 4 bolt block casting number 3969854. The book calls it a 69/72 396/402/454 2 or 4 bolt. Its already @ 4.250. What are the chances of it taking another .030..or is it something that will need to be sonic checked first?
It just seems odd that GM would cast a block that they
would ship as a 396 @ 4.094 and would be thick enough to bore to 4.250....or more.
The bore is dimensionally good where it's at but with the oem type 11.0-1 trw (427)pistons i am about out of valve clearance with a .620 lift cam. I am planning on going to a cam that has .670 lift....
I can have the pistons fly cut but i know they are really heavy anyway...And don't want to loose any compression but the selection for inexpensive 427 pistons @ std. bore seems limited.