915 valve question

I had 915 heads on my 318. With a 2500 stall converter and 4.30's, it wasn't any faster than my 318 heads. I learned 3 things 1) You need at least 3000 stall converter. 2) 9:1 compression isn't enough 3) You need to use a dual plane to get any decent throttle response.

The bigger ports ( intake) really hurt port velocity and without some big changes they won't help. When in doubt use the smaller of your cam choices with tight LSA.