Square vs. oval heads
Thread Starter
Instructor
Joined: May 2002
Posts: 216
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From: Savannah GA
Square vs. oval heads
I have been told by a retired race engine builder that you can get more horsepower out of oval port heads then Square or rectangle port heads. He proclaims that Leindenfelter proved this in one of his books on building race engines. Is this true? If this is so, why are all old corvettes with high horsepower ratings have square port heads?
Melting Slicks
Joined: Sep 2004
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It's all about velocity and volume. A slightly smaller port (oval) will build more velocity at a lower rpm, making more hp. However, it will run out of the ability to flow enough volume at higher rpm. The larger square port will still be able to flow at the higher rpm. This is dependent on the displacement. A 427 with ovals will probably make more hp below 5500. When you get over 6000, the rectangular will probably make more. Now if you're running a 540 or 572 cid motor, the rectangulars will probably have enough velocity even at lower rpm to beat out the ovals.
My overly simplified $0.02 worth.
My overly simplified $0.02 worth.
Team Owner
Joined: Feb 1999
Posts: 34,454
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From: Republic of Texas
Originally Posted by 68bigblock
I have been told by a retired race engine builder that you can get more horsepower out of oval port heads then Square or rectangle port heads. He proclaims that Leindenfelter proved this in one of his books on building race engines. Is this true? If this is so, why are all old corvettes with high horsepower ratings have square port heads?
It depends on the engine. Those square port Vette engines had solid cams that would rev to 7,00orpms with no problems. Oval port heads are great for torque that's what they are found on trucks and headvy cars (Chevelles) but run out of steam around 6,000rpms. The choice of head depends on the application and goals of the car. If you have a 427/454 that will never see pat 6,000 I would go with ovals, but on larger motors 454+ and engine that see 6,000rpms + rectangles will make more power.
