Intake manifold to head port mismatch

[WFarm]

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]

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]

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]

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

 

[Catbox]

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]

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]

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

 

[JD Miller]

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]

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

That must be what I was thinking of