Alright guys, not sure if this is in the wrong section or not. but, what kind of exhaust system (duel cat, single..etc) all you guys have with your LS1 engine? Please post some pics if you can. Looking to do a LS1 Swap sometime next year, and i've noticed most 4th gens with the LS1 have two cats...so i wanna see how it'd effect my emissions with only one cat or two cats or whatever

 

you need two cats as far as I know, because LS1 have OBDII which uses 4 O2 sensors, 2 before the cat and 2 after the cat.

 

i have a LS1 in my 88 ta i used a 98 setup that only has 2 o2 sensors that is what the painless harness sets you up for

 

You can reprogram the PCM to disable the two rear o2 sensors.

 

I'm running a custom Y-Pipe with the O2 sensor bungs welded in right after the flanges, no cats and O2 simulators that are fixing to get deleted. Then the rest is 3in. to a Flowblocker and a single 3in. outlet. Sounds decent.

 

Do the stock cats fit from a 4th gen. I have the manifolds down to the y pipe. I know i need to get a custom made y pipe though, but will the manifolds down to cats bolt up fine?

 

I used a 2001 F-body engine and got the stock cats from that car, couldn't get them to fit. Both were resting up against the floorpan when I bolted them up to the manifolds.

I had Mufflex cut the flanges off the stock cats, and reuse them to fab up my exhaust.

 

It all depends on what you want, and your local emissions.

All LS1 engines had at least 2 cats, stock. The 2001-2002 'Vettes and Firebirds even had 2 extra "pup" cats to improve their ability to pass emissions, which even got them into the "low emissions vehicle" rating in California!!

My '89 Formula had 2 cats to begin with, that would work fine. I am going to go that route for now (new exhaust system was just put on last summer anyway) with a custom y-pipe. HOWEVER........... the LS1 engines really like true duals. So that will be my first/next mod after the swap itself is down. I'm also going to try to fit in the pup cats, possibly, since I'm moving to CA very soon - it won't hurt anything.

Stock LS1 cats will NOT fit without custom work. At least one of the O2 bungs has to be relocated, some cars both front sensors have to be moved, due to space constrictions. I think it's a lot easier just to use our 3rd gen cat locations with good LS1 approved cats (like the Randoms - even CA legal).