For all you bbc guy out there, can yal answer this question? I dont know much about big blocks, but can you run a square port intake on oval port heads? I dont know what heads they are i think they are 325 horse 396 heads, the intake is a offenhauser cross ram.
I have done it the past. Probably not the best idea for performance though. You need to use square port gaskets.
From what ive heard it will work, but will mess with the flow, i was just wondering if someone could clear that up.
Rectangle port intakes will work fine on Oval port heads by using the rectangle port type gasket. Although it is not optimum flow. Guys have been doing this for 40 years and in many cases it picks up a bit of power by having the larger mainfold combined with the higher velocity at lower RPM of the Oval port heads. Figure it's OK up to about 468" and under 6,000 RPM
There was actually a very interesting thread on this subject on Speedtalk a couple months back. Short answer is yes, and the supposed negative effects on performance are alot less than you might think, if they are actually there at all. Put a head on the flowbench, and map the port opening with a velocity probe. What you find might surprise you. Some of this stuff is pretty counter-intuitive. Potentially, this is actually a really good thread.
I ran a 66 chevelle that way when I was a kid 325hp motor with a 375hp intake, ran fine, also a rayson craft flat bottom drag boat with an oval port 454 and a sq port tunnel ram.
I know for a fact you can. I had that exact mis-match on a 3400 pound ex Super Stock Camaro and it ran 9.85's at Palmdale. (That's 9.50s/60's at sea level) It ain't ideal, but it works.
I had a factory aluminum rectangle port on the 325hp oval headed 396 in my '66 El Camino. The intake was A+B puttied and port matched to the oval heads using rec port gaskets. I have no idea how close the original 325hp was to that advertised number and we did not baseline the engine, but it did make about 385-390 on a water brake with that mani, what would be considered an RV cam, and some work I did to the runners and bowls as the only mods. I did it just to see if it would work and to have a factory appearing aluminum manifold. If anybody knows how close that motor was originally to 325hp then you can take that number and decide for yourself if it's worth it from a performance perspective.
Yep, you can do it. I ran a 454 that way back in late 70's. My plan back then was to eventually swap out the oval port heads when I got the buck$ for a set of the rectangular port versions. I never did swap the heads out. The same engine later ran low 9's at 146 mph in a FED. I think that Falcon George gave the best hint at why this seems to work. Air velocity in the sharp corner radii of the rectangular ports is relatively slow.
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