I want to throw this out here and see what ya think. I am wondering how a Sq. Port Intake will work with Ovalport Heads? Anyone use this combo before. I have heard that it will work, so I checked the gaskets and it appears that there is a little restriction at the top of the runners but not at the bottom. Thanks for any input.

69,
I know of several people running that combo and they swear they run great, sort of contrary to what you would think !

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Please let us know how it works out. I've got an L78/L72 intake (square port) but want to keep my open chamber oval port heads. I was planning on port matching as much as possible by radiusing the top of the port on the heads. von

Thanks for your input and I will keep you posted on the outcome. I am also using a factory L78 intake. I plan on installing this combo within 2 weeks.

I've ran a combo like this, you have to be sure to use rectangular post intake gaskets, or there will be a vacuum leak. I'm sure it probably doesn't make as much power as an oval port intake, but everyone thinks you're running square port heads! It would probably help to radius the oval port out a bit, but I don't think there's enough metal in the port area to open them up all the way.

No question this combo will physically bolt-up, but I don't know how much effect reversion would have on performance. I guess the only sure fire way to tell would be to dyno this combo and then change to an oval port intake and dyno that combo to see if there is any difference.

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We used this intake on a '74 454, 8.5-1 compression and 049 heads. All we did was do a three angle valve job, machine the valve guides and install positive valve guide seals, add a Cam Dynamics 270 degree Energizer cam and a three inch exhaust with a balance tube and Flow Tech mufflers. The carburetor is a 750 Holley that still needs a little fine tuning. These aren't high rpm engines like an LS6 but to 5000 rpm the engine makes my L78 seem tame. The performance was a very pleasant surprise. Gas mileage was about 16 miles per Imperial gallon with 3:08 gears and dropped about 2-3 mpg going to 3:55's. A 280 Energizer might give a little more power but would be in an rpm range where these engines might not like to live. It would be interesting to do a direct comparison with an aftermarket high rise dual plane intake that matches the oval ports.

I wouldn't think it would work but I ran into a guy at Pomna who was running high 11's in a 67 SS with a 427 and he swore by it. HE said he's been doing it for years.

It does work, but I don't understand why. I know a guy who ran this combo of a sq. port intake on oval heads and when he switched to the correct intake (oval port) the car slowed down 3 tenths.

I didn't believe it would work either, but a buddy of mine GAVE me a manifold and said "just try it, it works!" It did. The improvement could have been any number of other factors, but I used that manifold for a long time and I liked it. One of life's little mysteries. If you have the manifold, all it will cost you is some time and the price of the gaskets. Just try it, it works!

How can it be? I just purcashed a square port manifold that someone was running on a street rod ( painted purple - yuck ) with oval heads and the port mismatch was HUGE. I find it hard to believe the flow would be so good running smack dab into the sides of the head.

well, this clears up the discrepency with the casting numbers on my heads saying they are oval port while my intake casting numbers indicate it is rectangular port. my car runs fine, so i guess it works.

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Ian McDermott
1970 Chevelle SS 396
Columbia University
New York, NY.
E-mail: havoc@graffiti.net
Web page: chevelle.dhs.org (http://chevelle.dhs.org)
ICQ UIN: 3923441

Yes the port mismatch is huge. The large rectangle intake port and the smaller oval head port look like they would never work, looks like a big reversion problem or fuel puddling problem but the head must suck the mixture into the smaller port.

I guess I'll put away my die grinder and never port match my manifolds again. All I can think of is that , at that restriction going into the oval head, the velocity must pick up some as the passage gets narrower and suck the mixture in. The moral of the story: BigBlocks are awesome animals that even reversion can't stop!

[This message has been edited by Gene Chas (edited 05-10-99).]