Streets has shown there are/were four-bolt 400 blocks as well as two-bolt 400s. Joe Butler says he only uses two-bolt blocks (whether they are 400s or 350s, likely 400 block for a 377, the issue is two-bolt versus four-bolt) for circle track racing with a 5.34 rear. To me that is enough to believe that the two-bolt 350 block is adequate for street performance at least up to the 380 H.P. I found in the book by David Vizard. The fact that Joe Butler can wind up a two-bolt block with a 5.34 rear in a competitive situation convinces me that at the very least a two-bolt block is strong enough to handle performance upgrades, but the points have been made that the crank+piston mass load and side motion are other issues. Since 350 H.P. looks like a dream to me and I will probably end up with only 250 H.P. with a torque cam and hopefully 17-18 mpg, it would seem to me that the two-bolt is fine for my needs and let others show one way or the other which is best. Still it seems pretty amazing to me that a circle-track racer would prefer and only use two-bolt blocks and be successful, so it looks like the two-bolt is pretty good after all.

Don Shillady
Retired Scientist/teen rodder