3" Collectors 2 1/2" cat back

[drochau]

Also posted this in tech. Hey guys can't deciede what to do. I have 3" collectors coming off my TPIS headers, and I'm trying to hook them up to my cat back exhaust which is only 2 1/2" diameter. I know I could have an exhaust shop make me some reducers to fit, but the car is a s/c 383 and I'm wondering how much hp I would leave on the table with that kind of restriction. Opinions? What did you do? Car is running no cats and I don't intend to run them in the future.

[mn_vette]

Well, the way I see it is that you've got three options

1.) Have a shop make the reducers for you and hook it up and you're good to go. $200 maybe


2.) Buy a new 3" catback system and have the shop make connection pipes for you and hook it up. ~$1000-$1400


3.) Buy yourself a welder, chop saw, and some pipe and make your own. ~$1000


If you don't want to drop big money( I know thats a relative term after the SCed 383) then I would live with the lack of hp.

If some people can get 10-15hp out of a stockish car I'm going to guess you'll be gaining 30+hp on your car if you upgrade. Remember, you can always upgrade later.

[tjwong]

Originally Posted by drochau

Also posted this in tech.

Hey guys can't deciede what to do. I have 3" collectors coming off my TPIS headers, and I'm trying to hook them up to my cat back exhaust which is only 2 1/2" diameter. I know I could have an exhaust shop make me some reducers to fit, but the car is a s/c 383 and I'm wondering how much hp I would leave on the table with that kind of restriction. Opinions? What did you do? Car is running no cats and I don't intend to run them in the future.

It kind of depends on what mods one has that determines how much gain a 3" would give you. In some ZR1s we have worked on there was as much as 30hp between a 2.5" Corsa and a 3" BB system. In a heavy breathing 434 there was about 30+ over the stock 89 system with a gutted CAT and Borlas. In a blown application there could be similar gains.

[drochau]

How about cutouts at the headers and then reducers to the cat-back system

[TONYDEE64]

Originally Posted by drochau

How about cutouts at the headers and then reducers to the cat-back system

I have 4" collectors that have electric cutouts coming right off of each collector at 90 degrees. The makes sure that my 3:" exhaust do not cause a restriction.