Hello all,

I have a set of fourth gen 00-02 manifolds, however, I was wondering if it is worth it to get LT's, specifically Speed Engineering? I would really like to use cats, which is why I got the manifolds in the first place. Is it possible to get cats to work behind LT's? I like nowadays catalytics, they don't rob too much power, and they get rid of the smells. I was searching around, and, on other sites, you see people saying "you can gain more than 20 HP!!" Not sure if that's really true.

 

Your signature says you've got a 4L60e. As do I. From my research, the answer is no. There's simply not enough room between the transmission and frame rails to put cats behind the LTs. If you had a T56, you'd be able to fit them.

You may also consider the mid-length headers that are out there and whether they could be made to work with cats. I ended up believing that this would be too tight as well as it didn't look like it bought all that much space, and I wasn't sure the gains were worth it compared to just running the manifolds ( which in all honesty are some of the better flowing manifolds, but they're no LTs still ).

For me, I'm going with a 4L60e and LTs without Cats for now (can do that in this state given the age of the car). Longer term, I'd like to swap to T56 and run cats.

 

Oh, boo. I forgot to take the fat auto trans into equation. Makes me wish I had more experience with driving manual. The only learning that was available to me was the big block Ford fuel truck at the FBO I work at. Only got to drive it a couple times.

Yeah, mid length headers would look awesome. But I have heard the same thing, that they offer little to no gain over the later iteration of the LS1 manifolds.

I am outside the emissions zone (by a mile or two), so I can also run cat free exhaust.