Hi, Ive got a 2000 automatic corvette. I just added a 04 ls6 cam, ls6 intake manifold, blackwing cold air and I hollowed out the cats. I just had it dyno tuned and it only made 319 RWHP!
Most people on this board with automatics and no heasders put down 340ish. The only thing different is I have the stock cat back.

I was going to see if buying a cat back would make up the difference and asked a few local tunners if this would solve my problem. They said the stock cat back on vettes is fine and aftermarkets hardly show any gains and that hollowing out my cats was the PROBLEM!

Joey at slp said that I would pick up 20RWHP if I put the cats back on because the engine needs back pressure! Anothersays to put a straight pipe through instead of holowing it out, because it causes turbulence and looses HP!
Which is better to put a straight pipe through or buy new cats from a salvage yard? If new cats then do I need to re do a dyno tune and have them turn back on the O2 sensors? ANd will I really pick up 20 RWHP?

Any comments would be greatly appreciated! Thanks

 

Who knows?

I've read a few articles about exhaust, which seem to explain it like this:

When cylinders discharge their load of spent gas, there's a momentary increase in exhaust pressure for that tube. At the same time, other cylinders' tubes have DECREASED pressure in the tube, and the decreased pressure has a vacuuming effect, pulling gas from the tube with increased pressure.

Seems to me that less restriction = better flow =morepower. But the dynomometer don't lie. So if I stuff a cork in the tips, will I get65 more horses???[sm=helpout.gif]

 

I think I answered a post of yours on this subject somewhere else. The stock engine's cam and tuning, etc., are designed inanticipationof a certain amount of backpressure from the cats and without that the engine does not run optimally. On stock engines keep the cats. On modified engines cats do get in the way of some additional power, but run them anyway:

I'd advise putting cats back on. First, it's the law but more important perhaps, in my view we all need to help the environment. Plus, I consider it cheating on a street car: if you are going to drive onthe street and race a "street car" at the track, run all the legally required equipment. I practice what I preach here, I have over 700 RWHP but still run cats on the street.