Well I was working on the factory exhaust manifold in May and it has been on a week now with no problems.So I will let you all in on it as it went very smooth start to finish.

First thing GMPP has a Extruded Honed Header that they will sell you for $300 bucks.Here`s a little secret it`s the same one that`s stock on all the 07-08 2.2 and 2.4 they removed the part # in 07 on the casting and they use a sticker on the box to tell the difference.

I wanted bigger gains in flow without buying a new header so I did a little research on polishing/porting exhaust manifolds.And came up with this modification to the stock header.

1st. step bolt your header to some 1/2'' plate and heavy angel iron or your header will warp and never fit again.

2nd you need to back weld the outside of the header with cast rod I went about 5 welds thicker go slow and only weld about a 1 1/2'' at a time on each side.Unless you can keep the header pre heated this will take 4-5 hours to weld.

You can see in the first 2 pic`s how much larger the lower outside is after welding.This needs to be done because when you open up the header you will be grinding out past the out side stock diameter.

3rd pic shows how bad the restriction is on the stock header the 06`s are worst.I will show you 06 owners what you need to do too your model at the end of the how to.

Pic`s 4-5 shows how much needs to be removed you need a air die grinder and a real carbide cutter this is NOT! a dremel friendly mod so don`t try it or think you can do it,it takes hours of grinding to get the final result.

 

In pic #6 you can see the final results of the amount of metal that was removed with the grinder.There is still alot of work to be done with sanding drums and flap wheels to smooth out and polish the inside of the header.

Pic # 7 shows that you all so have some work on the other end as the manifold gasket has to be matched to the manifold.This will be plainly seen once you remove the manifold from the head by the soot marks.

Pic # 8 shows the difference after the porting and polishing

 

very nice how to

 

Pic #9 shows how much more open and unrestictive the stock header is now the original only had an opening of 45 mm in the throat.The new reworked manifold now has a finished opening of 57 mm if I did my math right that is a 27% increase in flow which is huge over stock.

I did a 10 mile run at 50 mph before the mod and it was 37.6 mpg after all mods it went up to 41.4 mpg.As well as doing the header I also changed the intake to a stock 2.4 and added a CGS intake tube.

I have too say this little 2.2 is alive now and sounds great!!

Pic #10 just shows that the GM part # was removed so if you bought there GMPP manifold it wouldn`t have the same part #.They wouldn`t want you to think you just bought the same stock manifold for $300 bucks.

 

OK just for you 06 owners you need to do this mod even more but it is going to cost you some $ as you need to change your 06 cat. to a 07-08 cat.GM changed the location of the O2 sensor from the manifold in 06 to the cat. pipe in 07.

In the 1st pic you see the 06 manifold with the O2 sensor sticking in the way of the already restrictive opening.

2nd pic is the location of the 07-08 O2 sensor

All you need to do is change out your cat. with a 07-08 cat. remove your O2 sensor and plug the hole with a short 18 mm bolt and weld it in then follow the how to.

One other bad thing is the lower flange on a 06 cat. is only 53 mm and the opening on the manifold is 55 mm.The cat.flange on a 07-08 is a whopping 80mm

 

Here`s some link`s for you to look at so you don`t think I`am just blowing hot air .The 1st one list different levels of stock cast iron mods I went with the level 2 Super Shootout as you can see too have this done is very costly but you can do it yourself this was my first time and it came out great.
http://www.gesslerheadporting.com/me...5!OpenDocument
This one gives you some benifits for using your stock manifold http://victorylibrary.com/mopar/ci-man-tech-c.htm

This is some good reading as well on the GMPP cat. back exhaust only giving 1.2 hp increase over stock exhaust I will not be changing mine now after reading this.http://www.gmhightechperformance.com.../photo_15.html

 

Very nice! If I can live without mine for a weekend I will be doing this mod! Many thanks from the bottom of my fuel driven wallet

 

Here`s one more pic with the heat shield back on it covers the welds and no one will ever no what was done.My cheap silver heat paint is already lifting after 200 miles

 

Nice quality work, Mike...are you still tasting cast iron after all that grinding?

 

instead of replacing the cat pipe 06 model. you could drill and weld in a sleeve to screw in the 02 sensor?