Espescially important to port if you have a 92...

my 92 downpipe flange is/was welded on over a hole that looks hand cut in the rear manifold



93-95 rear manifold is cast so it doesn't have that restriction

That restriction would be good to get out, but porting the welds on the insides of the runners shouldn't be necessary on the 92'* either.

This should be a sticky.

Bill, what are your thoughts on L36 manifolds?

I like them. I've seen a few too. And they look really good when they're shiny.





Perhaps you should ask that in a topic that isn't so specific to a totally different type of manifold. Your manifolds aren't even remotely similar in shape, size, flow, or material.

Point taken!
Just did a search and realized this was an astonishing stupid question! Please disregard.
Thanks

Willwren did you port your heads yourself? Did you just enlarge the ends of the runners or the whole runners? Where is the smallest circumference of your exhaust runners now?

Oh, and you think porting like this isn't beneficial?





These are pics from DrJay'* build. He ported the runners out to match the inside diameters of the manifolds. No idea if that was a good idea or a bad one...

You killed your cylinder heads and performance. Who told you to do that?

The D-shaped port is there for a reason. It blocks the acoustic pulses that travel back up your exhaust from forcing exhaust gasses back into the cylinder on the next cycle. By removing the flats, you are causing reversion.

You should have only increased the WIDTH of the ports, while leaving most or all of the flats.

D-shaped exhaust ports are used for a reason, and generally kept intact even in performance porting of cylinder heads.

I chose the method I used to port my heads based on several conversations with some really good people at some very respected businesses. Edelbrock in particular, was a great help to me. It might be best if you do some internet searching on Reversion and D-shaped ports.

A search on reversion on this Forum might prove to be rather fulfilling, too.

This topic is about Exhaust Manifold Porting, not Head Porting. We need to get back on topic.