Windsor Senior Head potential

[juiceman]

for a 306 the jr's with a stage 1 porting would be your best bet. i would go to keith kraft for the heads myself. the sr's are a bit big in the ports and combustion chamber for a 306 and wouldnt give you the velocity you need. dont go by the flow #'s of the heads . a 306 will not consume that much air and will cause the motor to go slower. if you havent already bought the heads then go with the jr's. and change the springs since the ones that come from the factory are for a flat tappet cam not roller.