I have been hearing on here and elswhere that not having a cat on these will kill the torque is that true? I ask cause mine dont have one and it is just about gutless down low. i thought that this was just the engines way, but 2 things have prompted me to ask and one is that I drove an identical car to mine exept it had a cat, it had more Umph to it mabe not much but definatly able to feel it. the second thing is my car just got an minor exhaust leak and now its even worse. again i thought it was all just in my head but this is the 3rd exhaust gasket on this side of the engine and every time it got a leak it has done this. one day i go out and start the car wait for it to hit about 120* on the gauge and then hit the gas, get a good yelp out of it. the next day i go out to get in the car let it warm up and go to hit the gas and it wont pull its own butt for any thing. both days were of comparable temp,humidity and such. i went over the car and the only thing i could tell was different was the exhaust leak that werent there the day before.
Im gonna fix the exhaust leak for obvious reasons but should i install a cat or something that will create comparable backpressure? I know i read an article in the exhaust section saying its not backpressure really but whatever, Will it make a Difference?

 

i just pulled my cat for when i install the turbo,i didnt feel any noticable diff either gain or loss of power,the only thing it did do was make the car louder.
then again car has a stall converter and 4:56 gears,so even if there was a difference down in the lower rpm range i would never notice it.id just leave it, i could see if u were gonan turbo/supercharge ur v6 yeah then get rid of it.if it really bothers u that much and u think its hurting performance on ur na 6 swap it out for a catco hiflo cat or something simialer

 

It dont really bother me. the cat was already removed before i got the car and im not just making that up about the car running even more gutless than normal with the exhaust leak. All my friends notice it to. so i was just curious if the cat would also make a difference.

This was mostly a question out of curiosity.

 

no cat will make more upper rpm hp,but u will lose low end tq

 

Mine was very midly modded when the cat got pulled on mine. It did loose some around the town pep. I got better hwy mpg afterwards.

 

I've always thought the "you need backpressure" theory was an old (shady tree) mechanic's tale. However, in this era of oxygen sensors, it keeps a slight positive pressure ahead of the cat to keep any stray oxygen from entering, and throwing off the O2 reading. You say when you develop a leak, performance goes down? I'm not sure if more O2 is rich, so it cuts fuel, or the opposite, but, in any case, it's giving a false reading.

You mention gaskets going out constantly. When I pulled the left manifold off to extract a broken bolt, it wasn't flat. Had it ground flat, and guess what? The bolt holes didn't line up!! The heat distorts the manifold. There is a tool you can use to keep the manifold straight, but you have to use it BEFORE pulling the manifold off. Once it's warped, you can't bend it back. BTW, we ARE talking about stock cast manifolds, aren't we?

Cast iron heads did not come with a manifold gasket from the factory, but you can get a set meant for aluminum heads. Sounds like you may need to replace the manifold, or machine it flat, as long as the bolts line up. The gasket will fill in small voids, but with large spaces the gasket will blow out again.

Hope this helps,

Bob

 

im not woried about getting it macined or replaced it lasted 6 months this time an it only took me 15 minutes to change it . cost more to get that crap done than change it a few times. if i replace them im gonna get headers. now that i got that quieted down now i can hear that my belts are making a shuffing noise. i tightened them up but it wont go away.