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
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.
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).
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
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?
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!