I need a new cat. I have a 87 firebird formula 305 4bbl all stock. Can someone tell me what size inlet/outlet is on the cat. Called a few places and all they have is 3" and 2.5" which do I need? Thanks for the help.

 

Anyone???

 

Get a direct fit, save yourself a bunch of headaches (and probably some money in the end).

Checker should have it or can get it http://www.partsamerica.com/PartDeta...pe=145&PTSet=A

 

Ok, I'm guessing this is what GTA4ME's topic is in reference to, and I see you could get the Formula with the LG4.

For a reference, call Thunder Racing. They sell Random Tech cats, and they show a different part number for engine H than engines F and 8(which are 3" in and out). So engine H, which is smaller, is prolly 2 1/2". They're very nice people there, so ask them to confirm the size.

 

LAFireboyd, yeah GTA4ME is my son-in-law, Thanks for the info i'll try calling them tomorrow.

 

Thanks guys!

 

The stock inlet is 2-1/4".

Don't get a universal cat. They require fabrication/modification to get into the system, it just isn't worth the few pennies you save.