Found a bottleneck in this mail-order setup. These are the non-smog pump headers and y-pipe for approx $200 (about $98 ea) from jegs; header(s) p/n: 500-68470 and Y-pipe p/n: 500-17470.

Anyway, as most of you already know, the y-pipe features mandrel bent 2.5" pipes that lead from the headers to a collector-y, and then necks down into a single 2.5" mandrel section that then leads to the cat-con. The problem is where the two 2.5"s go into the single 2.5" pipe.

When they put this thing together, they shoved the single 2.5" pipe in about an inch into the y-collector facing the exhaust stream! Not only is the single 2.5" pipe a bottleneck itself, but there is a big gap around the pipe that results in a huge amount of turbulance that builds up as a result.

I solved the problem by cutting the y-pipe before where it necks down into the single 2.5" section and welding on a 3" mandrel 90 degree bend. Then, I simply welded a 3" mandrel 45 dergree end to the 90 which brought it to the cat.

This mod (or fix as I like to think of it) was worth a solid .3 sec gain in the 1/4 on my car, which now runs 13.1's @ 109mph on radials with lots of wheelspin but should be worth a couple of tenths on your ride as well.

 

Interresting. I didn't recall my y-pipe having that bad of a transition at the "Y", but then again I didn't really examine it all that close. Now I have more motivation for a new Jet Hott coated system.

 

You can't really tell by the outside, you have to cut it apart to see how bad it is. I have the piece here and will get a pic put online so you know what I am talking about.

 

When i got mine I took a real close look at how it put together,
my old Y pipe.. not THAT was a bottleneck!
mine was pretty much flush, maybe a 1/8" to far. not a huge deal, how far does your go past?
perhaps you got a faulty one.