i have just a stock 89 305 tpi,i wanna just put a exhaust system on it since the motor isn't really worth modding. so i have some headers and was gonna run a 2 1/2 in. single exhaust to my 80 series flow master, should i go bigger or no? only other mod i'll maybe tdo is a intake

 

I have heard that you will only need to 3in for cars running over 400HP to effect anything, running a 2.5 will be fine in your case, but in wouldn't hurt anything if you did go 3in

 

Go for the 3 inch pipe from the headers. Ypu'll never regret it.

Welcome to TGO!

 

A 2.5 inch pipe is too restrictive for even the weakest of V8s that came with thirdgens. A 3 inch pipe however will support you up to 400 hp, at which time duals is a good idea.

Go 3 inch if you want power and sound.

And those motors (LB9s) can be rather quick with a little work, so don't count it out. Besides if you wanted to swap to a 350 in the future, you'll DEFINETLY want the 3 inch.

 

Just placed a cat-back Flowmaster....3" all the way, thru a free-flow and dual Flowmaster exhaust off the Series 40.
My stock 89 IrocZ sounds magnificently "cool" and the performance, which is near equal to my 78Z has been upped a notch. I would say go the 3" route....it's just fine, me buddy.
Oops, just saw MadMax in that bitchin' Camaro...a very satisfying ending as he rode into the sunset. I almost did that a few minutes ago...but...then...I thought about the current gas gig!! Later, when "it's" straighter!

 

i wasn't sure since it was a 305. i am thinking of running slp loudmouths on it instead of the 80 series.so i know with headers,nocat, and 3" pipe its gonna be loud and hopefully sound pretty mean.

of course down the road a 350 or even a 383 or bigger will be going in.

thanks for the replys. hows the loudmouths sound ona 305?

since i have a firebird formula don't i have the 3.23 posi or no?
i have ws6 wheels and it says performance suspension on the dash so i was thinking i might have one of the rare ws6 firebirds or ws9 and someone said not sure tho

 

i out 3 inch on mine and it doesnt seem big enough

 

Mine had the 2.75" HO exhaust system, and it was ok... but changing to headers and a Hooker 3" system made it grow a massive pair (...so to speak )

 

i put my 80 series on today sounds mean but when i get higher in the rpms it gets quiter,maybe cause i have manifolds and 2 1/2 exhaust. getting headers soon so hopefully that'll make it louder.

will it ya think?

 

yes it does, the flowmaster sounds drool with headers and a high flow cat...u wont regret it

 

is that cuz you herd the clip of mine?

 

no
i've heard all the 4th gens with them and they sounded amazing and flowmasters always sound good usually. i think yah with the headers and 3" pipe i should be good.

i'm about to put a cold air intake on it,gutted the screen in the maf today. not sure if it applies but on my old car i put a conefilter on and my exhaust got a little louder.

 

I <3 HOOKER CATBACK

(PS- I AM I FORMER FLOWMASTER OWNER)

 

Just a little information: 1987 305 TPI Automatic came stock from the factory with a 3" exhaust. So why is it so big on later models?

 

Just want to tell you i had a 3 inch catback with a Dynomax Superturbo muffler (not too good) with a dynomax catalityc converter on my camaro in 98 when I still had the 5.0 in. At the time, I kept my original manifold and even noticed a nice sound improvment and a better flowing exaust...

But when I installed my 1 5/8 to 3 inch hedders, then the exhaust was really flowing and nice sounding

P.S. I have seen civic and other similar crap running 3 inch so don't worry for you V8, you won't loose torque compared to those punks

 

yah i wasn't sure since this is my first v8.its different going n/a since i only owned a boosted 4cyclinder and v6. from what i have been reading i shouldn't waste my time on my 305 cause theres not much to do. so i am gonna build a 350 up and just swap my headers and ect over when i'm ready to put that in

 

It was only 3" at the cat inlet. From the cat outlet on back is 2-3/4" at the most.

 

Original owner, 3' back to the muffler. Stock from the Factory. Did you own a new 87 305 TPI???

 

As 57kid said, it was a 3" converter into a 2 3/4" I-pipe with 2 1/2" muffler outlets. My L98 IROC-Z still has the original exhaust on it in great condition and even though it might look it, that I-pipe is not a true 3" piece.

 

it's not 2 3/4" and it is not 3" it has a 3" od is alot of spots but that is it. and the 2 3/4 is where it tappers down when it fits inside the "stock" muffler kinda strange how the factory made the pipe. but, alot of after market companys make the true 3" pipe



for one yes. leaving the cat it is 3" as it goes into the I pipe then it directly turns into a 2 3/4 untill after the bent then it is closer to 2 7/8" (maybe a little smaller not much though) until the axle which it then gets strange with the crushed spot and then tappers down after the final bent to a od of 2 3/4"