I'm going to try to port my stock exhaust manifold. I already ordered new gaskets from GM today for the exhaust. Does anyone have any info on this? A friend of mine is a machinist and he has dremal tool and a bunch of different shape carbide tips and stuff he said. I was wondering what type of gains I can get out of doing this? And is there anything that I should know. He looked up in the manifold when we had the pipe off putting in the wideband o2 and said it looked quite restrictive. Thanks

 

uh...i wouldnt bet on getting any gains, minimal at best...now porting the exhaust side of the head...that might would be a lil different...but not much...especially since you probably dont know what your doing...no offense or anything

 

What if you port the whole thing?

 

the runner's diameters for the stock header arent big enough to warrent this in my opinion...i mean, especially if you have a stock exhaust system, you arent going to see, or feel any gains out of this.

 

The best way to port & polish a head is very little amounts at a time while useing a flow bench to ensure that each cylindar flows equally. Through out the history of porting their have been better and worse ways to do it. really I would say your best bet is a CNC machining process bases off the results of extensive flow bench research. A home made port job on a big displacemnt V-8 (or V-6) cylindar balance wouldn't be that important. when you start dealing with forced induction you can do a lot of engine damage very quickly, which would not be cover under warrenty simply because the first step in an major engine warrenty job is to start by mesureing everything with micrometers.

The moral of the story- save money and buy the GM CNC ported ecotech head.

also I would have to agree that porting the stock exuast manifold probably wouldn't do any good.

 

I'm only talking about the part right above where the head pipe bolts to the manifold. He said that it goes down to like 1 3/4". I though it may help a bit since I have a smaller pulley. I was told every little thing you do to remove restriction from the exhaust will help Knock Retard. I have to talk the exaust back off anyways to put the new gaskets in so I thought I'd open it up a bit. My friend works with CNC machines daily and other such equipment. He is the main go to guy at this company, he is very smart and has ported heads,intake manifolds and many other things before. I'm not worried about my engine warranty either. So you guys don't think this would help at all?

 

The GMPP header isn't worth it imo.

 

And oh BTW I'm not touching the cylinder head. I'm only talking about the exhaust manifold itself.

 

Yes true with any engine the better the exaust escapes and fresh fuel and air comes in the more power can be made. I would say this, if the manifold is already off, it wouldn't hurt to open the manifold up a bit (indeed every little bit helps) but I would certainly say that to have a specific task of porting the manifold probably wouldn't be worth it. as far as knock goes yes better exuast gas scavaging will help reduce it