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Question on exhaust manifolds

Xp29h

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recently replaced a 383 hp engine with another. When I took the old 383 out, obviously pulled the exhaust manifolds off. Didn't give them much thought as the plan was headers for the new engine. Reason for the change was the 383 was not running well at all and couldn't get out of its own way..should also say 906 iron heads that had been redone and oversized valves and med cam.

Fast forward to yesterday. Looked at the numbers off the old e. Manifolds. Looks like the drivers side is an actual hp but the passenger side numbers show its a regular manifold not an hp (magnum)

That all said, here's the question(s) What if any performance issues would I have been experiencing with different manifolds? Would we have noticed any difference at all?

Thanks!
 
Flow. Non HP manifolds won't flow as good. Don't know if that'll answer your ?.
 
There are differences and that is that all HP manifolds have a 2 1/2 outlet and non HP manifolds are 2 inch outlet. Non hp manifolds are great for a bone stock engine, but that is about all they are good for. Find the right side manifold and be done with it.
 
Thanks for replies! I don't plan on using them at all. The motor that's in the charger has headers. Once I figure out what I really need to rebuild the 383, I'm sure I'll put headers on that as well.

I knew the sizes were different. I couldn't imagine that it would flow as well but wasn't sure how bad it would have been or even noticeable. With all the other issues with the motor, it certainly couldn't have helped.

Again thanks!
 
Interesting subject! I'm interested in an original '70 Charger with the 383/335HP and 727 trans. Have not been able to view the car yet. Would that engine/trans application have the HP manifolds with the larger outlets?
:thankyou:
 
it should have if they are still there.
 
Thanks e-440, the car is undisturbed/original except for new performance system with a X pipe midway from the manifolds back.
 
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