Porting the factory exhaust manifolds/crossover... people do that?

[johnny 5]

This may belong in the exhaust forum, mods can move it if needed. I was more interested in the NA input.

 

I didn't plan to do anything to this car, but porting factory exhaust manifolds can free up a few hp in some cases, and is almost a free mod if you do it yourself.

 

I'm curious how much room for improvement there is on the factory parts?

 

Some of the pics I've dug up show maybe a little room to open the inlets on the manifolds. I'm curious if the crossover and other flanges/welds have excess material that could be ground down.

 

So, has anybody done this or have any info?

 

I wouldn't expect there to be much gain, but anything is better than nothing.

 

I've seen some GM 3800 V6 manifolds that were disgusting from the factory and you could free up almost 8-10hp by opening them up.

 

 

This is something I've been kicking around for a week or so. Maybe if I get a slow weekend I'd yank them off and see what's what.

 

any input, good or impartial, is appreciated. thanks

[GEE-OTTO]

Well to start off with WE ( the 2.5i guys) have a solid piece exhaust manifold unlike the three piece turbo manifolds present in turbo Legacies up until the current year( the new LGT manifold is a single piece Equal length manifold).

 

If you want port the manifold it is a pretty easy task just lay the stock ( or w/e exhaust manifold) gasket over the flange mark with the material that is inside the inside diameter of the gasket then take a dremel and a grinding bit and little by little grind away the material.

 

It will help a little but without more air being pumped thru the heads with top end port n polishing and different cams you wont get much.