Square port intake vs oval port

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Square port intake vs oval port

Post  tiger on October 2nd 2012, 9:54 am

I watched the NHRA cars in St. Louis this weekend and watched several engines get torn apart and rebuilt. They all had square ports on intake and exhaust. Do the square ports make more power, if so why doesn't someone make square port heads for normal piston layout? BBC has the option!

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Re: Square port intake vs oval port

Post  dfree383 on October 2nd 2012, 10:02 am

429/460 BBF's do not come from the factory with square ports.

Only some Aftermarket heads come with them.

And no their is no advantage adding it to a factory Ford heads.

The difference in the Chevy heads is port volumn and valve sizing on the factory oval vs rectangular port heads.
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Re: Square port intake vs oval port

Post  tiger on October 2nd 2012, 10:34 am

Just checking cause I had a Chevy guy standing next to me say the square ports made more torq. I was trying to figure out why an 8,000 hp engine in a 2,200 pound car needed torq. Smile

I knew all the bbf heads from factory were oval and knew they could make some good power worked on. Just wasn't sure what the square port really did. I know most sbf came with square ports so I didn't know if there was a reason.

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Re: Square port intake vs oval port

Post  dfree383 on October 2nd 2012, 10:37 am

Old Tech.
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Re: Square port intake vs oval port

Post  tiger on October 2nd 2012, 10:42 am

Thanks

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Re: Square port intake vs oval port

Post  Paul Kane on October 2nd 2012, 11:58 am

tiger wrote: Do the square ports make more power, if so why doesn't someone make square port heads for normal piston layout? BBC has the option!
Chevrolet was the cheapo automotive line at General Motors. They cheaped out on their engine program more than any other GM product line. The SBC valve cover rails aren't even machinined, for example, they didn't significantly change their design(s) for 40 years, they essentially made only a "big block" and a "small block" engine platform for their entire vehicle line-up, etc.

Rectangular ports came about essentially to fit a reasonably sized port between the pushrods and so the port ends up being narrow and tall; it's yet another chevy a compromise. Sharp-cornered rectangular ports usually have very little-to-no activity at their tight, right-angle corners. Oval ports such as CHI's heads are rounded at the corners to minimize low activity areas.

If there are no compromises whatsoever then the perfectly round port is usually the overall best and has the best overall port activity for it's size, such as the Boss Hemi intake runner. Or the 385 Series oval port. Whether a fluke or intentional, the factory oval port 385 Series head is quite advanced for it's mid-60's development and release, thanks to the chamber shape, valve angles, spark plug location, and that oval-round intake runner....when those features are compared to those of the BBC or BBM of the same era.

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