they are 2v...iv had 4v and 2v 351c cars in the past and the 2v heads are much better street heads then the 4v. our old 72 mach 1 had a 351c cj and it didnt make power till over 3500 rpm but my 70 cougar with 2v heads and a 4v intake would eat the mach 1 right of the line....ps im near hershey pa