I would love to get a new cat back for my bird, but I may upgrade my engine from the 305 to 350 in the near future so I am thinking about holding off on the 'ol cat back.

I see that most cat backs are either 2.5" or 3". Seeing as I have the 305 engine, I would need a 2.5" cat back or else loose all my low end torque...right??

So, I should wait until I get the 350 in there before doing any cat back exhaust stuff.

Again, correct me if I am wrong.....

 

Go ahead and get the 3 inch. You shouldn't loose much low end if any- you might with headers. Many 305 TPI camaros came with factory 3 inch piping anyway, mine did.
Just my thought.
Good luck.

------------------
'88 RS (originally 2.8)
New 350, .040 over, ported vette L98s, ported stock tpi.
Old 305 injectors & chip
TES headers, 3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
(Damn the 2.8!)

 

Now that i think about it, the stock intermediate was like 2 and 3/4 inches, i remeber i measured it and the outside wasn't quite 3. My mistake.
But you should still be able to run 3 inch no problem, you may need an adaptor for the cat. I went from the stock system to a 3 inch edelbrock cat-back and it worked great, now noticable loss in the low end, and some gaind up high.

 

Yeah, Third Gens didn't come with a 3in. exhaust stock.

IROC-Z, your car didn't have noticably less Torque because its a 350, on a 305 there will be with a 3in. if its stock or almost stock.

------------------
Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

[This message has been edited by IROCZTWENTYGR8 (edited March 15, 2001).]

 

you migh loose a bit but I don't think it will be that noticeable. it will sound better however. so it is a trade off. better sound now with a bit less torque and then when you drop the 350 your set. or just live with the stock sound until the swap. I would probably do the swap now. I hate the way they sound stock. when I bought mine it got a new exhaust fast. I had an 88 pickup and I put headers and dual exhaust with 2chamber flowmasters on it. it was not very fast cause I had boggers on it but I loved the way it sounded.

 

My 305 is pretty much stock.Just added a 3in american thunder,3in catco converter,dual snorkel and k&n filter.I had better throtle response than before,and good gains up top.I am planning on switching to a 350 also.I do have slp headers right now but will wait and do those when I swap engines.

------------------
1987 Firebird Formula LG4,700R4,WS6,2.73 open rear
Current Mods:Flowmaster 3in. American Thunder cat-back,3in. Catco converter,L69 dual snorkel,K&N filter,roof console,Pioneer 1.5din cd player,BostonAccoustics 4x6plates,eclipse 6x9
ComingSoon! 350 crate motor(caprice),SLP coated 1 5/8 headers,edelbrock intake,edelbrock aluminum water pump

 

Milehighbird,

How do you like the sound of the american thunder on your 305, I to am thinking of going with that cat-back.

------------------
"Blaming murders on guns is like blaming spoons for fat people"

 

IROCZTWENTYGR8,
The 3" exhaust i was talking about was put on when i still had my old 305- I should have been more specific, and no i didn't notice any loss in low end. This is stricklty from sotp tests, never raced it before the headers.

 

U had headers and then put on a 3in. exhaust?? Whats mods did the 305 have when u put the 3in. on it, was it all stock or not??

------------------
Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

[This message has been edited by IROCZTWENTYGR8 (edited March 16, 2001).]

 

Check out my latest post for info on stock 305 TBI with 3" american thunder