Sb Head Flow Numbers

Not much except the 302 being a 318 head which would limit things in a bg way. All S/B heads flow reasonably close to each other as cast and new. Within a general area of approx 190-200 cfm intake.

The prize in heads (S/B) is how far they can go in ported form and how well they balnce out between the intake and exhaust ports.

Best as cast flow, in general are the X heads (Big valve) followed by the other letter heads.
Best balance in a S/B head *I beileve* belongs to the 308. It has exhaust port patterns of the W2 head.