Sounds like what I'm looking at tackling on my MC. Since dropping in the L67 ('04 engine into an '03 SS) I'd like to do a couple more simple items - Wizaired and the ZZP DP. I'm not sure if the cat back is necessary. I was planning on the 2.5" DP, but I see the 3" is recommended here for the SC engines. I'm still confused a bit - will the 3" bolt up to the remaining stock exhaust? Any that has done this, is it an easy install? I'm a big buy and can get under the car with my 6" home built ramps enough to do my oil changes, but never tried anything more than that.

 

3" DP for s/c engines. The DP will bolt right up to the stock cat-back. Aftermarket cat-backs are only for sound and they only help performance if you are making over 300hp. Installation of the DP is easy. Two nuts off of the back of the rear manifold, the O2 sensor, and the two bolts off the catalytic converter side. Replace gaskets and voila.

 

Nice, you likely saved me from buying the 2.5". And thanks for the confidence boost that I shouldn't run into any issues! Everything I've seen and read talk about the great fit of the zzp parts, so I'm looking forward to getting this done.

 

the downpipe will fit fine.

the stock downpipe is restricting and includes the ubend making it the most restrictive area of the exhaust so it will definitely help.

even if your not making 300hp aftermarket exhaust will help, it improves the air flow on top of sounding better or not so good, depending on your taste.

 

forget the dp and buy my slp headers in the sale section. 475 shipped and they're yours.

 

Why waste money on things that he does not need? That money could be better used for other go fast parts.

Please read: http://www.zzperformance.com/grand_p...les1.php?id=35

 

I think at this point my only question before I buy is regarding tying into the existing exhaust. This is a L67 out of an '04 SS sitting in an '03 SS. Since the L67 was mated up to the existing exhaust I'm assuming there was no difference in pipe diameter between the two. With an SC engine I'm looking at a 3" DP, but that won't have an issue mating to the factory exhaust in the '03 SS, correct?

 

that's good and all, but aftermarket exhaust will help, people have noticed gains by installing their exhaust here.

As far as the install of the downpipe, you should be fine with it lining up on the stock exhaust, i dont see anything that would affect it, the only thing would be if the engine was moved to the side or something and the stock downpipe is altered. there's a very small area for the downpipe to fit in so i don't think it would be altered much, so you should be fine.

 

The proof is in the pudding. I am hungry. Please feed me. Sorry, but the Butt Dyno does not count.

To the OP, the ZZP 3" DP comes to a 2.5" diameter right at the rear flange. It will bolt up to the stock N/A cat-back system fine. Don't listen to trewyn15 and drop $300-400 on a cat-back that you don't need. If you are going from N/A to S/C there are other parts that you will need like a HD-trans and axles, maybe some new motor mounts (poly), etc. Save your money and use it for that.

 

I'm with Condore on this one.
Only change the cat back if you really want to change the sound.
Don't consider it for performance, there are so many other mods that you could do with the money that will actually up performance on the L67.
Also, in my opinion the best sounding cat-back out there for the 3800 is the stock one...these things sound gross with an aftermarket cat-back.
Correct. The L36 and L67 cars use the same exhaust (the engine block is essentially the same, so the exhaust is identical from mani's to tips). The bolt-in downpipes that the vendors sell are tapered down at the cat-back flange to 2.5" to mate with the stock exhaust, so there will not be an issue there.