[cfmcnc]

Originally Posted by 65nss4spdGTO

If square ports or tall thin ports were most efficient, the Pro-Stock guys would cast the heads that way. That's why the lifter bore and block positions have been designed the way they are. With the success of the Edelbrock performer head, the best improvement made is moving the push rod out of the way and using offset stuff. If the lifter bores position didn't create this problem, we wouldn't need the offset stuff. It's all about usable real estate in relation to the bore size and bore spacing.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

Exactly Calvin... but we're working within limited spacings and positions...not creating new ones from the drawing board like the prostock stuff is . I downsized your statements a little to focus on what others here have missed in this discussion. It's all about AREA and speed for a given displacement underneath the cylinder head . And given the design of our beloved Pontiac limits the ability of scratch designed lifter postions and bore spacings...to achieve effective area to feed the growing displacements... the port that will work the best in a high end application will probably end up rectangular. As you need 4.100-4.300 of AVERAGE CSA to feed 535 c.i. at 7300 rpm (and that's conservative) and make any sort of competitive power to what's already out there...1,080-1,120 with cast intake and one carb . Pushing the limits with a Pontiac presents it's challenges...think cramming a large BBC port (conventional) into the Pontiac head. It really can never be big enough to keep up with the evolution . I think the approach angle is almost right for an oval...just not the area. I'm speaking of course of a max effort version of the head. Smaller c.i. or application specific stuff like Jim is working on is another story . Johnny