Heads...square or rectangle

[Essex29]

What's the difference? If my motor has rectangular on it now and I can get a good deal on a AZ Speed efi unit that is for square how much does it cost to swap...is it worth it?

[Craig]

"Square port" and "Rectangle port" are used interchangably. The intakes on the big block Chevy came in two basic configurations, Square (also called rectangle) or Oval. Exhaust are the same.

[Moneypitt]

I've seen square, I've seen oval, and I've seen the huge rectangular hipo port...... IMO the rec and the oval/sq are NOT interchangeable. I guess you COULD use a oval/sq port intake on the rec port heads, but going the other way, rec port intake to an oval/sq port head would seriously interupt the air flow. I think the real issue here would be combustion chamber sizes, the rec port were 117/118 cc, and the oval/sq were MOSTLY smaller, (there are ovals with 124 cc chambers, low compression 402 truck). Mixing port sizes CAN create problems with intake vacuum impulses to the fuel system........Just my .02........Moneypitt

[Craig]

Originally posted by Moneypitt
I've seen square, I've seen oval, and I've seen the huge rectangular hipo port...... IMO the rec and the oval/sq are NOT interchangeable. ........Just my .02........Moneypitt
I might have not been clear. What I meant is that I've heard the term "square port" and "rectangular port" used for the same design intake ports. Oval port intakes are different and not 100% interchangable. You can bolt the intake to the opposite heads, but there is some port mismatch.
I'm not 100%, but from what I recall there is only two designs for the Chevy production big block heads;
square (or rectangular) port
oval port (includes peanut ports)

[Moneypitt]

The rec ports are huge compared to the oval/sq port. The rec ports are rectangular, very distinctly rectangular. The sq ports are considerably smaller in port area, and could no way be mixed up with the rectangular port. What could be called oval, are very close to the sq port, with the corners radiused more. As I recall, the sq and oval port heads take the same intake gasket, I don't think the rec port gasket would even seal on the sq/oval heads. There is also of course, the open/closed chamber differences with both types,(I think), and as I said before, the 118 cc chambers on the rec heads were designed to use alot of piston to keep the ratio up, the smaller oval/sq ports usually had flat top, dished or very small domes due to the small chambers. If you had the heads side by side, there is no comparision. There is also the valve size limitations when using the lower performance head, and the area behind the valves limits much gain in power even if you open up the seats for the largest valves that will fit....... On and on and on... rec ports are in a group all by themselves. I'm sure someone here can list casting #s and port areas, as well as corect CCs etc...............................Moneypitt

[Beautiful Noise]

Oval Port
http://www.hotboatpics.com/pics/data/500/607Mis_Pic_s_015-med.jpg
Rect Port
http://www.hotboatpics.com/pics/data/500/607World_Heads_2-med.jpg

[Jordy]

Last I checked, and according to every gasket maker I've ever seen, there are only two types, roundy round or rectangle. Try finding a set of square intake gaskets. ;)

[Beautiful Noise]

Jordy if your referring to the Square Port gaskets on my Oval Port heads thats because I was running a Square Port Tunnel Ram,Waiting to get the Rect Port Head's which I do have now:)