AgentEran

So I have an LT4 that has the stock exhaust crossover in the form of a H pipe just behind the rear end.

A couple weeks ago I had the resonator cut off and straight pipe put in its place.. But I noticed the effect not to be as great as when I put a X pipe in place of my resonator on my '93, that does not have a H pipe like the LT4.

My question is, if I go back to get an X pipe on the LT4 do I need to somehow block off the stock H crossover in the back?

For reference, here is the stock H pipe before I cut the resonator off:

pologreen1

yes, mine had it.

Tom400CFI

You can put as many "H's" and "X's" in there as you'd like. After the first, the rest won't make any meaningful performance difference.

Kevova

The cross over (H or X) on the lt4 is too far back really to do alot. It might help resoundence. The cross over needs to be near the front where the resonator wound connect to front pipes.

grandspt

I have ARH headers with Cats and X pipe on my LT4 this is connected to my factory exhaust which has the small H pipe like yours, two years now and no issues sounds nice and no drone.

AgentEran

Id LOVE to get some ARH pipes.. but at 1800 dollars

Klondike

That little crossover in the back isn't really much of an H pipe on the LT4's. I think it is there more as a fastener/stabilizer to hold the pipes together than anything else. The hole under that little crossover, into each of the pipes is only about an inch in diameter anyway, so I don't think it does much.

MatthewMiller

Good replies above. Yes, that OE crossover isn't really doing anything. So to clarify, you are running two straight pipes in place of the OE resonator, right? IOW, it's now a true dual system all the way back? If so, then an X-pipe up closer to where the collectors converge just aft of the bellhousing will work, and the OE H-pipe in back doesn't need to be changed.

PLRX

There is perhaps 1 HP to no gains on that mod

AgentEran

Indeed, I have 2 separate pipes welded in place of the resonator.

AgentEran

Thats what is said when talking X pipes, but I really loved this mod on my 93. I dont know that it was worth 1 or 2 or even 5 hp, but it made the car run smoother at higher rpms, and the sound was alot more kick a$$.

I didnt consider the stock H pipe not really contributing and I thought adding the X pipe on top of it was redundant. But it seems considering the H pipe is not big or close enough that it would not hurt to add the X pipe. I just worried something I was not considering could go wrong in having both. There's some really smart/experienced cats here on this forum so I figured I would ask and see what came up in the discussion.