Intake manifold to head port mismatch

WFarm · Dec 11, 2024

I pulled the valve covers on the 454 and recorded the casting numbers on the heads. As I posted elsewhere recently, the engine is a 1971 LS5 365 hp originally in a Chevelle.

The vintage Weiand intake manifold (PN WCPSQ) is for the large, rectangular port heads. My heads are oval port (casting # 3993820, 1971 365 hp LS-5, Open Chamber, 113cc Oval Port heads).

The engine runs great; no known issues. Is this port mismatch to be concerned about?

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fast 99 · Dec 11, 2024

If it runs fine don't fix it. However, larger intake to smaller head port will be detrimental to performance. Square edge on head will upset air flow.

WFarm · Dec 11, 2024

fast 99 said:
If it runs fine don't fix it.

Exactly! If it ain’t broke don’t fix it, lol. But I was wondering if there was any long term detrimental effects. A reduction in performance is something I can live with.

fast 99 · Dec 11, 2024

I wouldn't think so. However, it would have more power [torque] with the correct intake.

Catbox · Dec 11, 2024

Not an issue.
Run it all day long.
The air in the runner will flow where it wants to be.

Could it be better, sure.
Will you notice the difference if you change just that one part, maybe but most likely not.

squaredeal91 · Dec 11, 2024

I agree and am a firm believer with the if it ain't broke don't fix it reality and practice it myself. However I seem to remember complaints about the 454 overheating during the summer months heat?

WFarm · Dec 11, 2024

Never overheated, but did have vapor lock issues which I addressed.

JD Miller · Dec 11, 2024

3993820: ’71 oval port, open chamber, 2.19- and 1.88-inch valves. Used on 402ci engine.

3993820: ’71 through ’84 oval port, open chamber, 2.19- and 1.88-inch valves. 454ci (car and truck)

Did you pull that weiand intake off that motor that someone wrongly installed on it. Or did you pull a oval port manifold off it and think that you want to put a rectangle port weiand intake on oval port heads?

Get the proper intake manifold

squaredeal91 · Dec 11, 2024

WFarm said:
Never overheated, but did have vapor lock issues which I addressed.

That must be what I was thinking of

Craig Nedrow · Thursday at 9:02 PM

Paul this came up on the chevy forum, and yes you can run a rec port intake on an oval port, but most times not the other way around, rec heads W/oval port intake as the top of the heads would be exposed on almost all oval port intakes. Some say that the rec port will slow the air down some, which makes since, as the air is flowing from a smaller to bigger port. You say it runs good, would it run better with an oval port? It would sure not be worth the money or time to find out. Run that thing!, and take your pup when you do.

Craig Nedrow · Thursday at 9:29 PM

BTW Paul, your pup pic was the catalyst of my pic change. Meet Stash, what a character, sometimes known as the trasher, crasher, dasher....yeah you catch the drift.

TotalyHucked · Friday at 9:13 AM

Yep, as stated it won't hurt a thing. Might be giving up a handful of HP and TQ due to the minor turbulence where the hard edge on the head is but I wouldn't worry about it

WFarm · Friday at 10:25 AM

Thanks for all the feedback! I plan to run it as is. If I ever do end up pulling the engine I may change things.

Intake manifold to head port mismatch

WFarm

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