You would be surprised what a good set of headers and decent exhaust can do for a small block, even shorties. You will have to do a little tuning in most cases to optimize for the increased flow. My brothers 1999 Tahoe 2wd has summit racing shorties for a 1996-2000 Vortec 5.7 and the Jegs Y-pipe along with the Magnaflow catback for the same application. We installed Thunderbolt cats into the offroad "Y" which I put in quotations because the Vortec 350s are dual exhaust to the muffler. His Tahoe actually has a Lunati 268 cammed L30 305 Vortec swapped into it when he bought it. He bought it cheap as the 350 had a broken crank when he bought it. Compared to the factory manifolds, cats and exhaust the 305 had a HUGE shot in the arm across most of the RPM range. We did the exhaust and a Volant cold air intake at the same time. Had to do a good bit of tweaking to the tune after to give it enough fuel to run properly. Taking the manifolds off also eliminated alot of heat being dumped into the heads and allowed us to put 2-4° more timing into the tune for even more torque. Fuel economy went from am average of 17 mpg in mixed driving to 19 mpg. It is more responsive even at highway cruising speeds and does not downshift on hills as often. 3.42 gears and 32" tall tires have it running 1,700 rpm @ 70 mph. It has always amazed me how little throttle you have to use to run down the highway. Runs around 18-20% TPS at 70 mph on flat land.Originally Posted by MAC
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