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Author Topic: Rectangular port vs. Oval port flow tests  (Read 3933 times)

povertyjet

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Rectangular port vs. Oval port flow tests
« on: July 03, 2009, 10:06:16 AM »
Interesting side-by-side comparison of these GM heads...





Interestingly, these same 781s also outflowed "out of the box" Brodix BB2 heads...those suckers are almost $1,100.00 each!!!
« Last Edit: July 03, 2009, 10:10:57 AM by povertyjet »
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GT Jets

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Re: Rectangular port vs. Oval port flow tests
« Reply #1 on: July 03, 2009, 10:40:27 AM »
I think we had this conversation already, the discussion started with dual plane intakes versus open plenums  ;)  but also the ovals are good for approx. 5500 rpm with moderate lift, I have used ovals for years and my uncle (veteran automotive machinist) would actually yell at me for trying to use rectangles on my boats and trucks as a kid...

I had a small block years ago that had the ports "rounded up" and the intake matched, up until 6000 RPM it was a monster, then fell off like crazy, but the cam was done right there also.

Most of the applications we use are going to be with .580 lift or thereabouts and under 5500 RPM, so the ovals are an obvious choice, especially with a hydraulic cam (mechanicals have an odd or just different lobe pattern). The amount of torque you gain is rediculous over the rectangles.

On the other side of things, I always thought a tunnel ram and a nice set of hogged out ovals would be a match made in heaven, just never gave it a whirl.....while going too and fro, dont forget about piston choice, very important to have a descent flat to flat area in the combustion chamber between the piston and head, this area is called "quench" and actually is used in reducing the flash area in the combustion chamber and lowers the piston temp. greatly reducing the chances of damaging detonation....


Geeze, I just wanted to say I agree with the idea of ovals, not break out in verbal diarreah :P

Peace out!

GT

GT
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Time to man up and yank it John!  :banghead:
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