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what is the real scoop on whether you can use an square port intake on oval port heads? would'nt this impede airflow/mixture?
 

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I am sure it would, but my car was set up like like that for 15 years before I took it apart for a rebuild.


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Rob, run a search on this. Unbelieveable but it works. The threads you find will tell you which gaskets to use.

My hypothesis on this is that as you go from the larger intake runner to the smaller head runner, velocity will actually increase as it enters the bowl area. That cant be a bad thing.

[This message has been edited by 427L88 (edited 05-03-2001).]
 

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I dropped my heads off at the machine shop today and their bracket racers, really known for great performance work. Anyway I'm looking for an aluminum intake to go on my BB 66 thats not to high and "ve been reading these posts about this also, so I asked them about doing this and they said sure it would bolt on but as far as performing well they said no don't do it.Thats Their opinion, and you know what they say about opinions, everybody has one. Well I sure have seen alot of positive comments about this on this site and I value T.C members opinions quite highly. So I myself am seriosly contemplating doing this myself as their sure is alot more lower profile SQ. port aluminum intakes out there for sale than there is O port. Just my opinion. Tony
 

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The practice of running a rectangular port intake manifold with oval port heads has been in use for over 30 years.

I myself run this exact setup. I also performed a back to back comparison between an Edelbrock Performer RPM oval port and a Edelbrock Performer RPM Air Gap rectangular port manifold. Both manifolds had been gasket matched with the Air Gap matched to an oval port gasket. With both manifolds a factory lifter valley splash shield was also used.

The net result with my combo was no significant gain in power or reduction in ET. However there was no loss in power or ET either.

On other BB combinations specifically in NHRA Super Stock cars gains have been found. Perhaps this swap responds better to a high RPM motor rather than a street/strip motor that doesn't see the high side of 6500 RPM.

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racer1320, What am I missing here? How do you gasket match a rec.port manifold to a oval port gasket? Aren't the recs. taller? I thought the width was the same but the height?

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70 Chevelle SS396/TH400/3.73 "What does not kill me, makes me stronger."
 

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Yeah, are you using that Moroso intake runner epoxy?
 

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No epoxy in the runners. Even after "port matching" the mismatch is huge! So much for all those that recommend having your intake manifold port matched to your heads.

Just lay a Fel Pro oval port gasket over the rectangular port and you will see there is material that can be removed. Ultimately you'll end up with a NEW shaped port that bulges out in the lower half. However the upper portion of the manifold's port will be blocked by the head casting(surface above the oval port).

Goes against all logic but it works!

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racer's '68

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[This message has been edited by racer1320 (edited 05-04-2001).]
 

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I thought that the most significant flow happens at the roof of the port? what would you hope to gain by touching the bottom of the port? I must admit I'm very suprised that you had no change in ET. what is your theory on this? thanx

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What it you were to open up the ports on the heads to get closer to matching. Is there enough material on an oval port intake runner to achieve this. I have wonder this for some time and have considered getting a set of 781's (cause that is what I have) and seeing the potential for grinding in the ports. Have any of you guys gone this far?
 
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