With any NA 3800 - the 2.5" is the way to go.

 

my ZZP downpipe is going to be installed monday and not today as in friday. the shop is workin on some cars that they put off this week and finnishin them up today. so monday it is

 

Is there a reason you didn't do the install yourself?

 

i dont have a lift and i i cant get under the car right to do it. if i had a good lift me and a friend could do it easily

 

Chichi -
If you've still got the original stock downpipe, then you'll probably want to have a decent breaker bar handy for the dp/catback nuts. Or an impact gun if you have access to one.

I only had a 1/2" craftsman ratchet so those two nuts elicited much cursing when I pulled my stock downpipe, and my car is newer than yours with less miles. (I ended up tapping the ratchet handle with a mallet to break the nuts loose)

I'd imagine that those two nuts are seized up pretty good as they are exposed under the car and are just plain steel.
A breaker bar and a good soaking in PB blaster or liquid wrench will make it much easier to pull them, and with an impact gun they would make you ask why the hell I had trouble with them.
You can get new nuts and studs at any parts store too for like $5 too. I highly recommend you have a set on hand.

Aside from those nuts, the downpipe is a super easy job. Like bumpin said it's only 4 bolts. The two that connected the downpipe to the manifold were super easy to break loose (I did spray them down with PB blaster the night before I pulled the old downpipe though too).

-Riggs.

p.s. Wear safety glasses when you pull the old downpipe. There was a bit of rust flying around from those catback nuts and since you'll probably be on your back you don't want that crap in your eyes.

 

lol yeah I was gonna hit up some liquid wrench and soak it overnight in a garage.

 

Depending how much water or salt has hit it he might just be ale to crack them loose. Worked for me.

 

I'm sure that they'll come loose.

Looking back I wish I would have done it the easy way, planned ahead and bought a breaker bar before I did the catback bolts.
Would've saved myself a lot of effort instead of using an 8" ratchet.

So, if you already have a breaker bar, or have access to one - use it.
If you have an impact gun, or have access to one - even better.



-Riggs.

 

I have some questions about the ZZP down pipe. I am interested in this mod but I am not sure about the options when ordering one. Since I have a SC engine I should go with the 3" bolt on with cat. This is my daily driver and I want it to be legal and not throw any codes. I need to have a system that will pass my emissions test. Option 1 should I select add rear O2 extension for 04 + GP or add rear O2 bung in off road pipe or no option because the pipe with the cat already has a bung for the O2 sensor? Option 2 add front and rear gaskets. I know this is all worded for the GPs and I know they changed the horsepower in those cars in 04 when the car got redesigned. I just want to order the right thing for my 05 Monte SS.

 

AwesomeSS -

Note that anything on ZZP's (or any W-body vendors) site that mentions anything different for 04+ only applies to the Grand Prix.

Pontiac updated the Grand Prix engines for 2004 (they are the Series III L32 engines for the supercharged), but the Monte Carlos and Impalas that are supercharged for 2004 and 2005 got the leftover series II supercharged engines (L67's).

Therefore, whenever you are buying upgrades for your drivetrain, note that the vendors apply the years to the Grand Prix only. Anything you need for your Monte Carlo will be the same as what is listed for the '97-'03 Grand Prix.

That said, what you are looking for in order to keep everything emissions legal is a 3" bolt-on downpipe with catalytic converter and o2 sensor bung.
All of the downpipes with catalytic converters have the rear o2 bung welded in. ( I attached the description from the zzp site on the bottom of this post)
You then have the option between mild steel or stainless steel.

You don't need an o2 extension harness, as the only o2 sensor on the downpipe is the rear sensor after the catalytic converter. The extension harness is mainly for people who upgrade to headers, as this will move the location of the front o2 sensor.

Note that since the catalytic converter on the aftermarket downpipes are high-flow converters, then your PCM is most likely going to set the check engine light with a P0420 code.
You will have the option to either have the code disabled in the PCM, or to use an o2 sensor emulator that will trick the PCM into thinking it is reading the same flow as the stock catalytic converter was putting out.

Feel free to PM me if you have any more questions. I just upgraded the exhaust system on my 2004 s/c SS two months ago, so I did a ton of research before hand.

-Riggs.