Does anyone have any experience porting stock exhaust manifolds? Is there anything specific to look for to take off/smooth out? I'll be eventually working on a pair of L69 manifolds. Any ideas? Pictures would be great too! Thanks folks.

 

Didn't do it myself, but a bud did.

Watch wall thickness. It isn't consistent, so you'll have to be careful where you remove material.

Best bet is to port match and smooth out radical steps only. Don't try to make headers out of them.

 

Hehe, you'll have to clarify that a bit more for me. I would guess that port matching is making sure the I.D. matches pefectly to the exhaust port, but what did you mean by radical steps?

 

He means don't hog them out to resemble the size of hedder primaries.

 

"Radical steps" are casting lines and machining bit stops that produce a shelf in the flow path. This is especially bad if the step faces the flow.

It's actually a good idea to make the manifold port slightly larger than the exhaust port (not a lot, just something like 1/8" or so).