I know its been covered time and time again. Ive looked through the faq's and multiple exhaust threads. I'm super confussed. Doesnt seem like i'm finding the answer i'm looking for.

I have a 89 vert NA. The exhaust is all rusted out and needs replaced. I purchased a new stock cat as well as a magnaflow muffler. They should be here tomorrow. I'm planning on making the exhaust single exit out the right rear. But i'm unsure of what size of exhaust I should put on it. I was thinking either 2.25" or 2.5". I'm also unsure if I should replace the precat silencer with just a straight pipe or get another silencer. Or if I should replace it at all. The car has 119k miles on it/ Thanks for any help on this.

 

Stock tubing from the y-pipe forward is 2.25", so you could use that size or 2.5".

In stock form it looks like this:

Exhaust manifold -> Pre-cat -> Pre-cat -> Main cat -> Y-pipe -> Mufflers

If you remove the y-pipe and dual mufflers, you'll need a section of pipe to connect to your single muffler. The exhaust manifold and precats can be replaced by a header, but not all will make it to the main cat (such as Racing beat's). Keep in mind that the more you open up the exhaust, the louder it will be. This is especially true with only 1 muffler.

 

Thanks. That makes it a lot clearer. I didnt know it had 2 precats before the main one. Should I replace those also with the factory setup or just replace it with a straight piece of pipe? I'm not trying to make it super loud. But I am trying to get it to pass emissions. Would it pass with just the main cat? Thanks

 

you can ditch the 2 precats,but you will need a Good working Main cat in order to pass emissions.(note,I had a cat that looked good but Found out some guy had hollowed it out,,it failed the emissions miserably,,that is why I say a GOOD working Main Cat!)

 

Well I bought a new stock main cat. So hopefully it will pass after I get the whole exhaust replaced. Its leaking everywhere. lol