I still don't get the whole "backpressure" argument. You want the lowest backpressure possible. If you have greater resistance to flow, that means more of the energy your engine makes goes towards pushing the exhaust out instead of spinning the crank. The problem that causes the power loss IMO is that the the diameter of the pipe is too big and exhaust velocity goes down significantly. The dynatech headers with their "small" 2.5" collectors and 2.5" Y pipe did GREAT on my 6.0 if that tells you anything.

 

the truck wasn't tuned till all the bolt ons were done, lt headers, ory, 3'' single in 3'' dual out magnaflow, underdrive pulley, low temp stat, shift kit with servos and tuned by Xessive. The truck has a 5.3 with 3:73 gears. I attended the tuning school cause I thought there might be a problem with the tune, but the tune is perfect. GMCtrk what do you reccomend me to do with my current exhaust setup? I was thinking about stepping my piping down to 2.5 right after the pacesetter y-pipe and into a single in 2.5, and single out 2.5 magnaflow, and take it all the way back under my bumper.

 

so a headered,pulleyed,tuned truck runs 14.4 in hot *** tx heat...id say you did pretty good.
Put a converter and slicks and some cooler weather and i bet you'll be in the high 13's

 

I'm wodering what affect the 2.5" will have,too.

 

backpressure is a myth

 

Amen.

Don't waste your money on changing your exhaust...its fine. Slap at least a 3000stall high quality converter in there, adjust the tune and find some cool weather for your 1/4mile run. You will be impressed.

 

Whatever you do do not step your exhaust DOWN from the 3" output of the Y-pipe to 2.5". That will create a restriction that the engine will not like. Exhaust methodology is to never "step down" as you route away from the engine, though you can always "step up" as an anti-reversion technique.

 

Vids of it in action? I had 2.7 60ft times with a 13.8 1/4 mile times so you haven't lost ALL your low end!!

 

I disagree with this. 3" Y pipe is huge on a 5.3L (unless we're talking about a seriously hopped up 5.3). Like I said, the 2.5" Y pipe and 2.5" collectors did great on my 6.0. There was absolutely no loss of SOTP power up top over the 3" collectors and Y pipe of the Pacesetter's when changing to the Dynatechs. The dynatechs seem to give me better pep around town and better throttle response.

 

So what do you think about this idea GMCtrk?