how big is the 3.4 y pipe outlet to the cat? i dont know wat size cat im getting yet... im pretty sure im getting the dynomax superconverter 289-15735 which should be 2.5" to go along with my dynomax 2.5" catback. i dont know if im looking at a muffler shop fixing the step-up or step-down in size.

oh yea... pacesetter makes headers for the 3.4L 4th gen camaros, will those fit on our cars? (mines an 86 2.8)

i did a search and didnt find these answers... and how is fuel economy? does it run smoother? or is it choked by the 2.8's intake? do i need to port it open to get OK air flow? thanks a lot... im still debating whether its worth it for my daily driver... thanks!

 

It doesn't matter; you'll be re-using your old 2.8's exhaust manifold and y-pipe. The 2.8 manifolds bolt right up to the 3.4. 3.4 headers bolt right up to a 2.8- but they won't fit the engine bay of a 3rd gen f-body, they need to be bent. 3.1Firebird did this to his car, and he wrote it up a while ago. It might still be in the archives if you do a search. if you can't find anything, let me know, I saved the message on how to do it.

 

the pipe is about 2.5", check out my pics. If you can wait about a month or so, I will find out if the 3.4 y-pipe fits or not on my car.

 

IF you do this swap,
YOU WILL GRIN FROM EAR TO EAR
Do a search for the 2.8 3.4 long block swap boogie.
Headers & etc.
Get your headers & get a CUSTOM Y PIPE MADE!
The 3.4 "Y" pipe is better.
IF you get it for free, cool.
IF NOT, get it done right.
I'm working on my low cost HiFlo 3.4 Y pipe.
IT IS UP TO YOU, to desire to do this swap correct and right.
Then the results speak for themselves.

 

the pipe is more like 2 1/4-2 1/8. compared it to the clamps for the dynomax tail pipe clamps.