The F head is the head we prefer to use as the basis for all our street performance and race heads. In stock condition the CR is too low and exhaust port flow of
all of the late heads that came into to US is poor, but both of these are easily corrected. The exhaust ports of the 72 and up heads, both FI and carbed can be modified to flow better than the earlier heads. The F head has the same superior
intake port with larger intake valve as the E head.

John
V-Performance.com