Im probaly goin to **** on for bringing this up because theres so many threads but i cant seem to figure out what set up i needs. I got a 88 iroc z with a 305 v8 in it and im doing the whole exhaust and this is the set up i found.

hedman headers and y pipe
http://www.summitracing.com/parts/HED-68470/
http://www.summitracing.com/parts/HED-17470/

magnaflow cat back
http://www.summitracing.com/parts/MPE-16829/

My question is do i need a 3" output on the y pipe to join it to the catalytic converter or can i find a cat with 2.5 in and 3" out. Is it better to go 3" the whole way through the system i would think it is but i didnt see the hedman y pipe offered on summit racing with a 3" ouput.

Thanks for any help in advance

 

These headers have a ball & socket connection so you need this y-pipe: http://www.summitracing.com/parts/HED-17478/. You will need an adapter from the y-pipe (2-1/2") to the CAT if your CAT is not 2-1/2" (mine was 2-1/4"). These are available from any auto store. The 3" CAT-back connection should bolt directly to the flange at the back of the CAT (no adapter neccessary).

 

The 17478 has a inlet of 2.5" and the 17470 has a 3" inlet to fit the header collecter of 3" and the inlet is a 3 bolt flange which should fit the 68470 headers.

 

The Summit data for the 17478 y-pipe inlet is wrong, I have install the 17478 y-pipe on my car (with 68478 headers) and the inlet is indeed a 3" ball socket. Anyway, Hedman doesn't make any 2-1/2" outlet headers for our cars that would require a 2-1/2" inlet y-pipe . . . IMO you do not want to mix a 3" ball socket header with a 3" flat flange y-pipe, it will leak!

Give Hedman a call if you want to verify this yourself.

 

I decided to go with hooker 2460 headers and 16767 y pipe because its supposed to be a better y pipe

 

I don't think you can go wrong with either brand. I have the Hooker 3" CAT back (http://www.summitracing.com/parts/HOK-16820HKR/) and they fit tight, but do not rub anywhere. I really like their sound, too.

Good luck with your build.

 

thanks ill post how it goes when i gets it