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Originally Posted by snowdog
it all comes down to back pressure. more back pressure is good for low end torque and less is good for top end power.
how its measured i have no idea.
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You NEVER want backpressure, you wnat high velocity to promote torque. Backpressure equals restriction, restrictions are NEVER good in an exhaust system.
Some pople repoort torque loss when installing larger tubing, this is because the exhaust pulses lose velocity, tehrefore low rpm scavenging falls off.
FAST035, those tiny 1 7/8" headpipes sure are laughable, esp since they have pretty bad bends in them as well.
I have also seen some 1/2 ton Tahoes with teh larger 2 1/4" headpipes.
It seems like the Vans get a lot of teh goodstuff. Larger exhausts, L31's driven by 411 PCM's, L31's with TBI fuel sysetms on top. List goes on and on. I'm glad that all this van stuff applies directly to my truck. Goodold GM interchangeability.
peace
Pauly
97 GMC 2wd RCSB 5.7, s10 2700 footstall, Hooker 24621hkr LT's , 2.5" cats dual 4"pipes exit B4 pass. side tire, custom driveshaft 3.42 G80 FIPK MAF descreen GM/Mercruiser Marine intake manifold 29lb LS2(EV6) injectors Ed Wright PCM(best mod), LT4 KM 14.8@94mph 2.007 4000lbs 122mph