Of course I have aftermarket heads and cam as well as shorty headers and a Flowmaster cat-back. I'm getting ready to get rid of the cats(as soon as I access to a lift again) and then do a dyno. But I was just wondering what kind of gain should I expect? Not going with long tubes just yet, but will have shorties and no cats. I have heard not to expect much as well as a gain of 30 or so hp.

Since you have dual cats, I'd be surprised if you pick up more than 10HP.

One of the guys in our club had a similar set up as yours with shorties and no cats and then went to high flow cats and longtubes. dyno'd and ran about the same with the shorties and no cats.

I don't think the loss of power due to cats are worth the environmental damage it might possibly do... also, if your caught, the fines can be HUGE.

I removed my cats and installed shorty headers on my relatively stock car (K&N amd Muffler elims), and I gained 33 rwhp and 42 rwtq. I went from 14.01 @100 mph to 13.56 @109 mph. So would say there is a lot of power to be had by removing them.
Tony

I'm all for saving the environment and all, but people do a lot worse things than removing cats that there are either no laws about or are not enforced. I say if you live in a place where you can get away with it, do it.

pollution from removing cats is a concern? bwahahaahaha


go picket/protest a Volcano, or some of the Forest Fires...

im gutted mine and had a seat-of-the-pants noticable gain...plus it sounds cooler... http://www.corvetteforum.cc/ubb/smile.gif
actually, ive been told that since it is so big inside the empty cat now, to just leave it there for stock appearances, as a complete elim pipe wouldnt do anything more.

I have a simple theory. It is called "responsibilty".

I will not ever recommend that a street car be de-cated. I did it once for a short while. I needed to accumulate the cash to replace. So a test tube went in. And no, I did'nt gain a ton of power (It was an old toyota, anyhow)... if anything, I pickup power when the cat went back on!

If I had an older car and was customizing it, I would seriously consider adding cats.

Remember one thing... most modern engines are designed to deal with the increased backpressure.

KLRVET - If you gained that much power from removing the cats, you had a problem with the old ones. Random tech makes a nice high-flow replacement.

GIJoe - I believe that one person can make a difference. It is not as simple as protesting a forrest fire... to be honest, I hope your joking. because the comparison is absurd.

I looked into the Random cats. No way in hell I'm going to pay $325 EACH. http://www.corvetteforum.cc/ubb/eek.gif That is $650 that I could use to buy ceramic coated long tube headers. What are they thinking? Has anybody actually bought a set of these? Anyway, they don't do emissions testing here, so that is really a non-issue(if they do, i can always put the cats back on).

Bought a set of the high flow cats from IRS for $89.00 each. Believe their was an article comparing the high flow cats with no cats--No cats were about 3-5 HP more.

On a single cat you can expect a 2.5% increase. (i.e. If you are producing 400 HP the cat is costing about 10 HP.)

I bought my high flow bullet cats from Catco very cheap. These suckers flow well. I can blow dust off the ground from 6 to 8 feet when I rev it. But the test is looking through your cat with light behing it. With the stock Chevy cats the light was almost not there. It was barely visable. But with my new cats you could see a lot more light and objects too (looked like the vision of a drunk person). Random Tech is all about advertisements. Car Sound makes their cats and are way cheaper. Catcos are cheaper still. They are all basically the same. I would personally run cats. Your motor needs back pressure and at least you can pass a cop without feeling guilty. I feel guilty when I pass a cop with no front plate http://www.corvetteforum.cc/ubb/biggrin.gif. Here in So. Cal. they pick long streets with no "get aways" and block them off so traffic moves at 5mph in one lane. The cops have a rolling emissions tester parked to the side. They pick on a lot of cars and they would have put me on but I was not in my Vette http://www.corvetteforum.cc/ubb/smile.gif. It would suck to be caught with no cats or dummy cats. If you want cheap headers buy Hooker Longtubes that are ceramic coated from here:

http]//www.carpartsonsale.com/parts/search.cfm?keywords=true&matchpartial=tr ue&useall=true&manu=all&string=HKR-2149

This is the cheapest price for new ceramic coated headers for the C4.

I just removed my cats from the GS and installed long tubes (actually the car is at the exhaust shop as I type this getting the pipes/flanges made to mate the headers to the cat back) I have to pass an emmision test where I live but Im getting a show car waiver. My car has a whopping 7800 miles on it so I highly doubt that Im contributing to the pollution problem with the little that I drive my car. Some of this Emission $hit has gone too far, these tree huggin SOB's want to put catalytic converters on mowers and motorcycles also. Im all for being enviornmently friendly but some of this stuff is completly absurd.