rexcellent

What is the size/diameter of the stock Y pipe and stock catback on an LT1 car?

teke184

ypipe i think is 2.25"

stock catback is 2.75"

KPZ-28

The '96-'97 y-pipe got upgraded to 2 1/2" for 10 extra hp.

rexcellent

alright, thanks.

krillformula

What size is the stock cat? The outlet that connects to the catback?

canuck94z28

Yes the 93-95 size is 2.25 and the catback is 2.75 .The 10 h.p increase when going to a 2.5 y on the 96-97 though seems overly optimistic as i went w/ a Borla 2.75 y and gained very little and i remember reading that the Borla y was a good alternative to headers which is also false.The only other thing that may have caused my gains to be poor would be a dying opti that has been giving me problems for the last 2-3 yrs or longer!