I am rather new to engine performance and would like to know if open or closed port heads are better, and if oval or rectangular port heads are better. Thanks for your help on my last post, My 396 will make 400+ hp.

There has been much discussion and debate on this topic as of late. I would suggest rather than reviving this topic you do a search on it or on my user name and you'll find the answers and opinions your looking for.

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racer's '68 (http://www.homestead.com/headsupchevelles/page13.html)

10.83@123MPH n/a
1.45 60 foot
3900 lbs.

Do a search on the subject and you will get just about any answer you want to hear.
I think if the car sees any street use run oval ports unless a factory L78 or any factory rec port head engine.
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Brett
'67
SS396
clone

In summation, if < 510 ci, and <6400, then oval....
RECT PORTS ON EVERYTHING ELSE ! http://www.chevelles.com/forum/biggrin.gif

Open chamber theoretcially more efficient. However you can get a high compression ratio with flattop pistons and the smaller closed chambered heads. You need a domed piston to get the same compression ratio in the larger open chamber. Theoretically the dome causes less effective combustion. This is real nit picky and I wouldnt dwell on it at all other than to know that there is a big difference in combustion chamber size and the type of pistons used in either application.

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Gene Chaas
Gold Member 62/ACES
67 SS 427 (http://www.chevelles.com/feature/october2000.html)

[This message has been edited by 427L88 (edited 03-06-2001).]

How come you guys couldn't make it that simple last time? http://www.chevelles.com/forum/biggrin.gif

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Steve Beuth

69 Malibu ZZ4-350
93 Camaro Z28
99 Silverado
Chevelle pics (http://hometown.aol.com/zz69chevelle/myhomepageauto2.html)

Thanks guys, that was much needed help.

It should be added that if you go oval and want the performance of rectangulars or better, make sure you do the valve upsize and port work discussed in the other threads. If you just do a stock oval head, you will be disappointed.

Red Label

For performance use - you need to put big valves in the oval port heads or just buy new Merlin Oval port heads. Either option will cost about the same.

Like Bob said, except if you need closed chamber heads. No aftermarket company makes those. So if you are looking for around 100cc chambers, you can not buy the Merlins. The chamber is too big and your compression ratio will drop way low. This is my current predicament. Anybody have a set of 290 heads for sale???

JR

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My 70 Chevelle (http://www.angelfire.com/pa4/jim/)

Jim, they're all over the place and I know the local resto shop had more than 1 pair. Call Bob at Camaro Specialties, tell him I sent you, 716-652-7086. It is a resto shop so they price accordingly.

Gene,
thanks for the tip. I plan on hitting some local places, then maybe the spring swap meet at Englishtown. If I can't find what I want, I'll call Bob.

Thanks again,
Jim

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My 70 Chevelle (http://www.angelfire.com/pa4/jim/)