Ok I want to put an edelbrock catback on my car its a 1991 formula with a single cat lb9 auto. I need to know what size the factory y-pipe is because they sell a kit for the 2.5 and the 2.75 cars.

Also I need to know where I can get a cat to fit the original y-pipe and then exit into 3 inches for the new catback because I cant seem to find one on summit. Thanks for any help.

 

anyone guys?

 

ok after trying to do some research I think that i want catco 4115 which is 2 1/4 inlet and 2 1/2 outlet and then get the edelbrock catback that lists for 2 1/2 pipe because after looking at a list of cats for our cars it seems they all have 2 1/2 outlets. Can somebody confirm or disagree?

 

take the headers of the rs should be 3" collector on the y-pipe right then buy the 9118 cat and edelbrock 3" catback (the one listed for 2.75" cars)

 

not ripping the rs apart keeping manifolds for now.

 

put the manifolds on the rs

U ARE A CHODE

 

what is the difference between the two kits anyway if they are both 3"?
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too much work i just want to bolt this trash on.

 

wells its either getting shitty 2 1/2 system now or wait and get 3" if you get that converter and catback now you'll be forced to get the bad direct fit headers or just now headers at all and edelbrock is cheaper then hooker by about 10 bucks

 

both kits have 3 inch pipes thats why i do not understand the difference between the 2

 

were the catback bolts to the outlet of the cat is 3" the other is 2 1/2" so yeah both i pipes are 3"

 

I have the stock y-pipe on my 91RS, but the muffler shop welded on extra tubing to expand it to fit a 3'' catco high flow, and a 3'' edelbrock RPM catback.

When I got my L98 swapped in, the y-pipe was expanded from where the 2 pipes connect, so it is now the same size from the joining all the way to the cat.

The initial install at the muffler shop cost me like $80, and it only took less than 1/2 hour.

 

does anybody know where I can get an exhaust reducer that goes from 2.25 to 3 inch? I looked around some with no luck.

 

If you go to an exhaust shop, they can probably fab something up for you.

 

Here is a picture of what I did for Tim:

(A little crude but you get the idea)

 

All I did for now was get a 3 to 2.5 adapter then a 2.5 to 2.25 adapter to make one adapter when put together...this way it will be ok until i get headers.