Having engine swap done. A ffriend is doing it for 400.00 with the help of his brother in law. His BIL is a drag racer and builds 9 sec firebirds. I purchased a freashly built 350 turbo with shift kit and a heavy built 350. It should be going in tonight and I was told the manifolds will not work. I ordered some hooker 2054 for the car. I am planing on going to Flowmaster cat back. How much power will I lose doing this. I think the current setup is 2 1/2 " Also will I need a new Y pipe. Tryting to get a jump on things to get car back sooner.

 

Do you mean Hooker 2055?

What, if any, power loss you'll experience going from some sort of long-tube with dual 2-1/2" depends mightily on the engine you're building. If you were considering using stock factory cast iron manifolds with 2-1/2" duals, the answer is you'll see a boost in power output with the Hooker 2055's (which include a y-pipe, by the way).

 

OOPPS Hooker 2460

 

There is a y-pipe available for the 2460's, but it is inferior to the one you get with 2055's. My advice would be to send the 2460's back and get the 2055's. The price of the 2460's and y-pipe is almost as much as the 2055's, and by the time you modify the 2460 y-pipe to make it "as good", you'll have spent more than you would on 2055's. Same story with fabricating a y-pipe for the 2460's.

The rest, as they say, depends upon the engine going in.