I have these heads , if I had it to do again , I would have taken them and had the ports opened up a little more especially on the exhaust side and maybe mill them a little to bring the compression back up since they have 64cc combustion chambers .......they flow 213/int and 134/exh @.500 valve lift ....stock heads are 156/int and 116/exh ....just for comparison GT40Ps are 196/int and 139/exh........