Cutting the cat/losing power
 

I have all original exhaust on my car and was going to get true duals, mufflers, and headers soon. But I've been told by people that I will lose alot of power if I take the cat off because it loses alot of backpressure, is this true? I thought it would have to go anyways to get true duals since the 2 pipes go into 1 cat and then back into 2 pipes for the mufflers. Anyways I was just curious about whether it would do anything or not, Also If I put long tube headers on it, will I have to make any modifications besides cutting the pipe shorther at the motor?

Lack of back pressure is an old BS story. What you need is pipes of the proper length and diameter to produce sufficient exhaust gas velocity, and prevent exhaust reversion while the exhaust valves are still open during the intake stroke. Long tube headers will increase low end torque, while shorties will increase top end power. In both cases you need a free flowing exhaust system behind them in order to get best results. In many cases improving exhaust flow may require retuning the engine to take advantage of the increased efficiency.

If that "removing a cat converter makes you lose power" myth was true, then you would have to say that the addition of a cat enhances power.
Sorry, it ain't so, and that's not why cats were put on in the first place.
Next, I suppose they'll start putting cats on dragsters to make them go faster too!

I figured that it wouldn't have any effect on it, but just wanted to be sure before I do anything.

Actually, I have seen engines (stock LS6 in an '02 ZO6) where removing the cats will result in a slight (5-10 HP) reduction at high RPM. I think this is where the myth comes from. But you have to remember that in these cases this is removing cats from a factory engine that was built and tuned to have the cats on the car: this is not the same as asking what would happen if, with the cats off, you retune the car (the car gains the power back and a bit more (which it probably wouldhave gained even with the cats on) although in my case there was not a lot there with the stock cam). The way to get the rightamount of backpressure is is use proper length and diameter exhaust headers and that way you get it at the widest possible RPM range.

yeah but lee, you have to remember the cats on an 02 vet are an entirely different animal. its a high flow high effecient cat. and the engine is programed to run with these cats and so forth. changing and not reprograming could have a loss in power
the cat on a 78 camaro is a hog that sucks up power and really didnt do much. and like the other guys said. you have to have the proper pipe size to have the correct exhaust valve flow and back pressure. alot of guys love the throw on 3-3 1/2 inch pipe systems for a low end 305 , that one not only look stupid but two don not function well....

Concidering the first time I heard the myth was about 1983 I don't think that was the origin of it.

i have cut the cat off my 79 305 and without proper exhaust, there is no backpressure, which takes away from the "kick" off the start and the power down the road. the 350 isnt as bad when cut off but still needs the backpressure. ive done this twice and you get the same results. just put a good exhaust and muffler on it. you will do fine

So what size pipe is the best size to get the right amount of pressure out of it, and what kind of mufflers and headers do you recommend? I want flowmasters but don't know if they different types make much of a difference besides maybe a little deeper sound. And as for headers I want to put long tube's on it, Would shorty's be better or am I fine with long tubes?

shortey are used most often.