Bendeco

I read somewhere that a guy ported his original exhaust manifolds. He said that they had lots of extra metal from the welding and just cleaned them up. I don't remember if it resulted in any gain? Would that be worth the trouble?

cv67

Wouldnt feel it but sure doesnt hurt
(I wouldnt if its stock or very close)

ToniH

I don't know what your motor is but if its L98 with the stock stainless shorty headers I doubt there will be any measurable difference - just lots of work. If you go through the pain of removing the headers I would recommend installing something else instead of the originals for actual gains (some money needed, but less work).

I mean if this doesn't effect anything then surely grinding little welding off surely doesn't:

ghoastrider1

Interesting test Toni. Thanks for posting.

John A. Marker

To really answer your question.....we need the year of your car...or fill in your profile with the year of the car. Some years have tube exhaust manifolds and others have cast iron. My 85 had tubes. I gasket matched the inlets to the exhaust from the head. Had to weld up some areas and also ground off the air tubes that were sticking down inside. No noticeable gains, but I felt better knowing that there was a smooth flow out of the head without obstructions.

BOOT77

Crushed tubes has nothing to do with flange fitment. Many upgrade headers to not realize the only thing they are doing is making the port holes match less bad and I say that because the tubes are often too large, large enough you can crush them and not loose power You need a bigger circle to not obstruct a square.

Just port match the manifold to the head and make sure your gaskets fit. Don't grind out too much unless you have a welder to weld up the tubes on the outside.

People will tell you constantly it's not worth it, but all those worth nothings add up to something. Use what makes sense and not peoples opinions or flawed experiences.

Kevova

Many years ago LMSC didn't allow tube headers extrude honing exhaust manifolds was a common practice to get an edge. As tube headers have become the norm, unless you were is some kind of restricted class racing I don't think it would be worth it