sbc heads
I have a 355 sbc 10:1 four bolt main. I had a set of 340292 64cc heads with a performer RPM non-air gap. We bought a set of 180 AFR street heads, 68 cc combustion chambers, and put on a Motown single plane. The difference was incredible. You could actually feel it in the seat of your pants. I would say anywhere from 50 to 100 hp easily. This is in a street 57 Belair hardtop, which is a very heavy car to start with. We did do some minor port matching on the intake to match the head ports. Other than that, it was a straight bolt-on. An added benefit was that the detonation we had with the iron heads went away. Anyway, I feel that the price of the AFR heads was money well spent. That's not to say that other heads are not as good or a better value, but I would not trade these for anything else. One person's opinion. Mike Pscenicka (mep)