LS1 Headers, 4L60E, and cats?
 

Trying to get started on my LS1 swap again after a long hiatus and need to pick out exhaust components. I'm not against swapping other stuff to make things work as well, though I'd have to sell what I have that's barely used. I currently have a Spohn tubular K and the typical swap parts for the 4L60E to mount up well. Stock LS1 manifolds fitted up, but it seems a shame to have all that clearance and no headers.

Question - is there anybody who's made LS1 + Headers + 4L60E + Cats work? I'm asking about cats just to avoid the smell that removing cats brings. It's not required for emissions in my state, given the age of the car.

Looking through old threads, someone may have done this with mid-length headers but the install pics are broken. I'm open to ideas!

Thanks,
Jon

Re: LS1 Headers, 4L60E, and cats?
 

Been doing more searching. Wondering if it would be feasible to use the Hooker Blackheart headers and run a very small high-flow cat inline after each. There are some mighty slim high-flow cats (3.5" OD) available. Fitment is a concern, but so is heat output from the cats. Anybody have experience putting cats so near an automatic transmission?

Re: LS1 Headers, 4L60E, and cats?
 

I did put ceramic 2.5" inlet/outlet cats after longtube headers, but that was with a T56. I simply don't think there is enough room beside a 4L60E without hanging very low.

If you're set on cats, then 4th gen direct fit headers and 4th gen cats are probably the only way you're going to get there. Unless, of course, you cut out the 3rd gen frame members beside the tranny and figure out some other way to tie the chassis together.

Re: LS1 Headers, 4L60E, and cats?
 

I don't see the installation of cats behind the Hooker Blackheart headers being possible with any automatic transmission. The collectors are pretty much in the location where the cats themselves need to be positioned to optimize ground clearance.
https://cimg4.ibsrv.net/gimg/www.thi...b0b5bccd03.jpg

Re: LS1 Headers, 4L60E, and cats?
 

Thanks guys. I was hoping that a high flow CAT with a really lower outer diameter could be put where the pipe is immediately after the longtubes. Jegs has some really small diameter cats that I was hoping could work, but I can understand that area is really tight and you don't have much length to play with either. Stainless works has a couple (got model numbers from Jegs, but dimensions from Colorado Speed):

• 842-RTCMM (10-3/4" overall length with 4" Body dia., 3" ID inlet and 3" OD outlet)
• 832-RTCSLIM (9-3/4" overall length with 3" Body dia., 2.5" ID inlet and 2.5" OD outlet)

If the longtubes aren't an option, then I was looking at the Hedman mid-length headers that are "direct fit" for thirdgen LS swaps. Not many folks on here have run them, but it does look like you'd be able to put a CAT where the collectors are on the Hookers, though you're also making a the turn in the same spot and trying to get the alignment right to follow the frame members like the Hookers do...

My previous setup was using F-body manifolds to pipes that each made immediate 90 degree turns and ran outside of the frame rails for the cats and then came together with a Y post-transmission. It worked, but that 90 degree turn makes you wonder... If I could make headers + cats work without spending an arm and leg trying (and failing) I'd like to (to the point of selling my pre-Hooker parts and buying all of their gear to match up and make it as seamless as possible).

Maybe I just need to go and smell a car without cats that doesn't have obvious other issues (like running pig rich) to understand whether it's bearable to be without them. Sure is complicating life. I just can't go off and do this and have my wife (or kids) refuse to ever be around the car again. The older I get, the more this is becoming something I want to share with my sons.

Re: LS1 Headers, 4L60E, and cats?
 

If they dont appreciate uncatted exhaust they're not car people lol. Its like sweet perfume for us car guys:)

Re: LS1 Headers, 4L60E, and cats?
 

Geez, man, how old are you?
In my day, half the cars were uncatted. I loved the way that they smelled. If you really want your sons to be gear-heads, then I think un-catted is the way to go; let them know what it used to be like.
And as far as your wife: who's wearing the pants in your house? (Joking! Or maybe I'm not...)

For the record, my wife had the converter taken off of her Firebird before we started dating (the whole reason we ever met is because we both have Firebirds. Who ever said that cars can't get you p*ssy?).
That's one of the many reasons she's my wife now.

Re: LS1 Headers, 4L60E, and cats?
 

LOL. Ya'll are great. One thing's for sure - there's no room for cats beside the auto transmission. Even if they would fit, they'd get so hot that you wouldn't want them there anyway.

I had a long talk with a good friend/fellow thirdgenner last night about this and have realized that I have NO experience with non-catted cars that aren't full-on race cars or that have serious AFR issues. All of these have smelled so strong that it's been a turn-off (think driving behind a car, a full 1/4 mile back, and wishing you could find some fresh air). His advice was that on a modern fuel-injected engine that has a stock or mild cam, the smell should be minimal and nothing like his own car (high overlap, ~700 HP, very rich smelling exhaust). He recommended that when this lockdown stuff is over and car shows start up again, I need to go and gain that experience. I'm hoping that he's totally right and I can just forget about the cats.

Re: LS1 Headers, 4L60E, and cats?
 

Unless your tune is way off, you shouldn't have any offensive odors, it'll just smell different than a catted car.

You know what I really miss the smell of? Uncatted diesels. Reminds me of riding around with my dad on his tractors when I was a kid.

Re: LS1 Headers, 4L60E, and cats?
 

I love my 2003 F-250 W/7.3 diesel, nice waxy smell.