musclecar70sfan

iTrader: (1)

Hey guys, I got a stock 91 Trans Am convertible with a 305 TPI LB9 engine other than an AC delete. I'd like to get a full exhaust (headers-back) with a 3.23-3.42 rear end (right now I have 2.73) and maybe those wider diameter TPI runners. I'm not looking for a race car but do you think I'll feel a gain? My 0-60 is about 8 seconds and what kind of 1/4 mile do you think I'm running now? What do you think I'll run with these mods? Thanks!

v10viper04

YOu need more than just runners to let the TPI breath.. Intake porting is a MUST with those engines. If you do exhaust and runners it might help you a little but it won't be much faster if any. You might feel faster b/c the car is louder... Your probably a mid-high 15 right now... I would say...

bbtaz97

iTrader: (3)

headers and exhaust will def wake up the car for sure.. Runners need to be combined with porting the plenum and some kind of intake work . I have a stock intake that was ported out to match the runners , something like that. i woudl do all of that first before swapping to the 342 gears.

fly89gta

iTrader: (1)

Skip the runners for now, not gonna make a huge difference on a stock 305 with an otherwise stock TPI set up.

Headers and exhaust will never hurt....one of the first things you should do(aside from suspension)

musclecar70sfan

iTrader: (1)

Oh gotcha, thanks guys! I'm happy with my car's handling, so I'll be rebuilding my front end with factory-spec parts (already have em, just gotta find the time). As for the exhaust upgrade, do you think I'll see a difference on paper? Maybe a few tenths shaved off the 1/4 or 0-60?

bbtaz97

iTrader: (3)

anytime to get free flowing headers and exhaust you will def see better track times even with a 305 as well as better throttle response . it will also pull a bit more in the upper rpms. one thing to keep in mind when your doing headers is what size to get.. when i had a 305 i got 1 5/8 and now that i have a 350 to put kinda wish i had gotten 1 3/4 but those are really overkill for a 305 and u will actually loose torque when putting them on a 305 so just plan out things is the point.

musclecar70sfan

iTrader: (1)

Thanks for letting me know since I forgot about pipe diameter. Some day I'd like to drop in a 350 but for now I'll do what's best for the 305.

tpi305

Hooker 2055's come with a new y-pipe (no fabrication of one needed), the one that originally came with the car sucks. I don't really know what they can shave off a 1/4 mile time, but before I had mine on, I had trouble getting past 115. After I put them on, I hit 122 and it was still climbing. They really do make a difference. Plus, the sound is nice. I also went from 16.8 mpg at best to 17.8-18 mpg.

I think headers are suppose to be good for anywhere between 10-20 hp depending on your setup. I have headers and 3.23 gears stock and it's still a 15 second car. I don't really know if those runners would help you or not, I think a stock 305 gets plenty through the stock runners, but I don't really know. A cam would really liven things up.

v10viper04

Runners will do nothing for a TPI if the manifold still has stock size bores.... Your getting more air into the runners BUT you can't get the air out of the runners and into the motor any faster than stock b/c the intake itself can only flow so much... If you are going to get runners go all the way. (new intake or port existing) IMO

fly89gta

iTrader: (1)

Especially on a 305, especially naturally aspirated.

musclecar70sfan

iTrader: (1)

Yeah I heard about the hooker 2055's but those things are pricey. I see that headers come in different lengths, with shorties, medium, and full lengths (at least according to summitracing.com). What are the differences?

v10viper04

Shorties are the most common in the third gen f-bodies, they are short headers(hence the name) and usually dump near where the factory manifolds do. Long tube headers are less common but the better choice IMHO. They are harder to install and sometimes the a-arm brackets have to be clearanced for them to fix. My set i did not have to clear the brackets, i run hedman LT's and they clear by about 3/4 of an inch. I'm ok with that... The medium length headers i have not dealt with, nor do i know of any for a third gen f-body. Long tubes dump near the transmission cross-member. (usually a Little before), You will have to fabricate a custom y pipe for them, or have a garage do it for you. There are plenty of ppl on the site who run long tubes, including myself. I like my long tubes but i'm sure there are others who would rather run a set of shorty headers. I'm sure others will chime in shortly....