[chiphead]

Originally Posted by mgarblik

3.55 rear gear, fairly heavy car, OD on top of that. I would go for the extra cubes and the torque that goes with it. As Steve mentioned, a set of "ported" 670 cylinder heads could mean anything from a loss of 40 HP, to a gain of 80 or so HP. That is a pure guess without flow sheets and a good idea about the person or shop that did the work. "Just making iron shiny doesn't gain you anything." A quote from Joe Mondello, one of the best. RIP.

I'll agree with that. Not having flow numbers is a big deal. Steve25 and I spoke several times on the phone when I was roughing in the 670s by hand. What I learned is, you just dont make the port bigger. You have to shape it a certain way to guide the airflow through the port. For the exhaust, you raise the roof of the port, as the pressurized air tends to follow the outer surfaces as it makes the turns. The gut reaction is to lower the floor of the exhausts to gain port size, and that's the wrong approach. So thats the sort of thing you need to look for in ported heads without numbers. Does the port shape look correct? Has the pushrod bulge been cut back properly? Are the bowls blended properly? Are the ports symmetrical, is there enough meat to seal off, is the finished surface correct, etc.

[Elarson]

For street, go with the extra cubes for more torque and more fun stoplight to stoplight. If you posted in the race section, I'd say better heads for more peak horsepower.