So I've been building a 6.0 for this 93 C3500 dually I had. Finally got it running. It's basically a stock rebuild, 6.0 .030 over, 317s, BTR Stage 2 truck cam, TBSS intake, 90 MM throttle body. Nothing else of major mods, using stock manifolds. I street tuned it before the dyno, runs fine. First pull, 220 HP, now this is a dyno dynamics dyno, but STILL. Did a little fuel and timing tweak, 235 HP. I thought to myself something isn't right here, I had a 04 2500HD with a 6.0 on this exact dyno and bone stock it made 250. So I decided to take the muffler off that was on the truck, voila 40 hp! So obviously that was a restriction, but even after a little more tweaking the best I was able to get was 279. That just seems awful considering I've seen stock 6.0s minus longtubes in a car make 320! THis thing with a better cam, better intake etc I figured would make 300-310 ish. Was able to pull my graph up and compare from my old 2500 and this thing is actually falling off power wise earlier then my stock truck did? I'm at a loss, I know everything is assembled right, the truck runs fine, it just feels kinda slow, it was mainly built to tow stuff with, but I'm slightly afraid now, it only made 302 FT lbs, all these runs were made in 3rd gear with a locked converter also. AFR was 12.6 and timing was about 23-24, any more and I started to see KR.

 

What does the exhaust system consist of? My 2000 2500 stock had dual 3" back to the muffler. Does this '93 have something as capable?

How about the air filter and intake tube?

 

The exhaust is basically taken straight off a newer 2500 truck, except its merged into a single 3". The air intake is a 3.5" tube with a dry flow filter. Obviously the muffler I had was WAY to restrictive. Putting a muffler on it now.

 

I would go with a 4" intake tube to compliment you intake/throttle body setup. Do you recall what your MAP readings were at high rpm?

 

Single 3" exhaust is probably not enough either. I had a cutout clamped into a single 3" exhaust on my heads/cam 6.0 and it used to blow the exhaust apart when I beat on it.

 

Power falling off early with everything else the same points towards airflow, either in or out or both.

 

Did you say its a dually? Thats a lot of drivetrain loss right there.

 

The pulls were done with a single rear wheel which takes a ton of rotating weight off. I'll amke some pulls without the air intake to see if that makes any difference, I'm just disapointed, I figured it would make more power, not 100 more but 20-30 more.

 

You could always post your tune and log files here if want extra eyes on them.

 

Even with a single wheel in the back of a dually you still have a heavy *** rear end and the one wheel itself with an E load range tire is still a lot of weight to get moving.