streetbad

Where can I buy a stainless 4" intermediate pipe?

Injuneer

Contact Mufflex. They sell a mandrel bent 4" IM pipe that they bend in their shop, but I've only seen it in aluminized mild steel (had one for many years, no rust). They might be able to make one for you in stainless steel.

Mufflex Performance Custom Exhaust Systems Trenton, NJ

TitoPR221

Depending on the power you are making you may be better off with a 3.5" system, good for up to approx. 500 RWHP (Vizard). The 4" will be a bear to fit over the diff. I have a 3.5" from Stainless Works and it was a very very tight fit.

I also used a Burns 2 to 1 collector, with 3" inlets and 3.5" outlet. I run long tube headers with 3" collectors and a modified y-pipe with high flow cats.

427 RWHP and 388 RWTQ (ft-lb) through my exhaust and it passes emissions tests.

If interested send me a PM and I'll send you details.

streetbad

Has to be 4" for me, I am interested in the tuning (sound) that dia. 4" volume will provide. I have a 3" Y-pipe and 3.5" stock type muffler I am going to run. I could use the extra flow also for~800 hp.

Injuneer

Running the 4" IM pipe over the stock upper panhard rod brace is basically an interference fit:

streetbad

Thank you for the picture. I find that very exciting, a 4" will give me hopefully what I need. How much HP do you think you lose with a 4" with 800 flywheel, compared to open headers? I am willing to give up quite a bit so I can run more often without "guidance" from the "man". The muffler I have is only 3.5" so I think the whole 4" intermediate pipe will quite it down some and lose some heat and backpressure before it hits the muffler.

Injuneer

I pulled the 4" Mufflex off, and substituted 3" Borla XR1 race mufflers bolted to the collectors, and a 3" pipe on each side toward the rear axle, with turndowns. My original Y-pipe had flanges, so I could run 3" CarSound cats, or drop them out and replace them with the Borlas wen running leaded fuel.






There was no measureable difference on the chassis dyno. Buddy of mine pushed 1,125 flywheel HP through the 4" Mufflex and had the same results.

The big advantage was saving about 50# of excess weight. Although I also would have had to have a new Y-pipe made when I installed a Gear Vendors O/D on the TH400.