ok, obviously there is no replacement for displacement. I have a fresh built 331 stroker engine and a small blocked 40,000 miles 351(came out of a van). Both have the same roller cam, performer intake, holly 650 dbl pmper, and main girdle. I'm interested in road racing, opentracking the car. Can the 331 perform as well as the 351w? Those who have used both, other than displacement, what are not so obvious differences? By the way, the 351w is a roller, using the conversion tie bar lifters usinf a 5.0 H.O. type cam not the small base cam. Thanks everyone.