tri-power oval port vs square port

[Ted K.]

I have a 68 427/400 with the incorrect 4 barrel carb and manifold. I have a complete tri-power manifold and carb set up but it is off a high hp car with square ports. The 400hp has oval ports.
Will the square port manifold bolt up to the oval port engine and if so will it work, and what gasket set should I use?
Thanks

[Ridge K.]

Re: tri-power oval port vs square port

I have a 68 427/400 with the incorrect 4 barrel carb and manifold. I have a complete tri-power manifold and carb set up but it is off a high hp car with square ports. The 400hp has oval ports.
Will the square port manifold bolt up to the oval port engine and if so will it work, and what gasket set should I use?
Thanks

Ted, I have been told by several people that trying to seal these up with special gaskets, etc. , .....is simply looking for a headache.

I've never tried it myself, but trust the people that have told me their experiences.
Perhaps someone who's actually had first-hand experience will comment.

Ridge.
(have a '67 427/400)

[Gary K.]

Re: tri-power oval port vs square port

If you decide to not proceed with the #3919852 intake manifold setup let me know - I have the square ports and have been fishing around for that sucker for a long time. Another note, I currently have a big holley 780cfm 4bb setup and the car runs like a rocket, but it's definitely not original setup.

[Patrick B.]

Re: tri-power oval port vs square port

I would think that a stock type gasket for for a square port manifold would seal OK. But with such a big mismatch between manifold and intake ports, gas may pool in the manifold when trying to start the engine when cold, and the air flow at high RPM may be affected.

[Tim G.]

Re: tri-power oval port vs square port

[Wayne M.]

Re: tri-power oval port vs square port

Ted, I have been told by several people that trying to seal these up with special gaskets, etc. , .....is simply looking for a headache.

I've never tried it myself, but trust the people that have told me their experiences.
Perhaps someone who's actually had first-hand experience will comment.

Ted, Ridge --- Here's a pic of a GM oval port gasket overlaid on a square port "842" aluminum head. This combo doesn't work, obviously, because of the open gap (to the atmosphere) at the top. However the sides of the runners line up, and there is a small lip at the bottom junction with the intake.

For 5 years I ran a square port "963" intake (with square port gaskets) on "215" oval port heads. I never noticed any vacuum leaks or stumbling -- of course I didn't take it out to the dragstrip, where there would obviously be a difference .

[Ridge K.]

Re: tri-power oval port vs square port

Ted, Ridge --- Here's a pic of a GM oval port gasket overlaid on a square port "842" aluminum head. This combo doesn't work, obviously because of the open gap (to the atmosphere) at the top. However the sides of the runners line up, and there is a small lip at the bottom junction with the intake.

For 5 years I ran a square port "963" intake (with square port gaskets) on "215" oval port heads. I never noticed any vacuum leaks or stumbling -- of course I didn't take it out to the dragstrip, where there would obviously be a difference .

GREAT pic, Wayne.

Thanks for posting. I was told it required some very fancy footwork involving homemade gaskets, and often problems popped up.

Ridge

[Michael F.]

Re: tri-power oval port vs square port

Easier to just buy an oval port manifold.

[Joe L.]

Re: tri-power oval port vs square port

The thing that I've always wondered about is if an oval port intake manifold could be used with rectangular port heads. Oval port gaskets would, of course, not work but I'm not sure if it would work with rectangular port gaskets, either.

[Michael H.]

Re: tri-power oval port vs square port

I have a 68 427/400 with the incorrect 4 barrel carb and manifold. I have a complete tri-power manifold and carb set up but it is off a high hp car with square ports. The 400hp has oval ports.
Will the square port manifold bolt up to the oval port engine and if so will it work, and what gasket set should I use?
Thanks

I think it was Bill Clupper that posted here several years ago and talked about a friend of his that ran a new L88 short block with oval port heads and big port intake manifold at the drag strip a few times before he could afford new correct big port heads.

He also mentioned that the car wasn't much faster with the new big port heads.

I know of a few more 11-1 CR small port head cars running around with big port intake manifolds. Big low and mid range torque numbers.

[Patrick B.]

Re: tri-power oval port vs square port

I think it was Bill Clupper that posted here several years ago and talked about a friend of his that ran a new L88 short block with oval port heads and big port intake manifold at the drag strip a few times before he could afford new correct big port heads.

He also mentioned that the car wasn't much faster with the new big port heads.

I know of a few more 11-1 CR small port head cars running around with big port intake manifolds. Big low and mid range torque numbers.

It's hard to imagine what oval port heads had combustion chambers that would not interfere with L88 piston domes, either open chamber or closed chamber. Also the compression ratio had to be pushing 14 to one unless closed chamber L88 pistons were paired with 73-74 454 smog heads.

[John M.]

Re: tri-power oval port vs square port

A rectangle port intake will fit and work on a oval port head using the rectangle port gaskets, you cant use a oval port intake on rectangle port heads.

I had my dads old 1970 ford 3/4 pickup as a tow rig for my race car 20+ years ago, it had a 1970 390HP 427 oval port motor with a rectangular port 435HP tri power it ran great if the temp outside was 80 or less.

[Ted K.]

Re: tri-power oval port vs square port

Thanks for the comments and to Gary, The manifold actually belongs to a L89 project car that I have and I will keep it with that car, but I am loosing interest in the project. The 1968 L89 car might be availabe in the near feature if anyone has a interest,
Ted

[James H.]

Re: tri-power oval port vs square port

Ted,
I just came across your thread about the square port tripower bolted to your 400hp. I can tell you personally that it works just fine with square port gaskets. I've been running mine that way for 2 years now and haven't noticed any problems. I would rather have the oval port manifold but the cost has always convinced me to keep it. The ovals always bring more money.
I sure would like to know though if the correct manifold performs better than my setup..
Let me know how you've done since November.
Jim

[Ted K.]

Re: tri-power oval port vs square port

Ted,
I just came across your thread about the square port tripower bolted to your 400hp. I can tell you personally that it works just fine with square port gaskets. I've been running mine that way for 2 years now and haven't noticed any problems. I would rather have the oval port manifold but the cost has always convinced me to keep it. The ovals always bring more money.
I sure would like to know though if the correct manifold performs better than my setup..
Let me know how you've done since November.
Jim

The initial responses discouraged me from trying the set up and a NCRS member had an oval port at a reasonable price. Solved the whole situation.