So I recently bought another LS1...a 1998 Trans Am. It already has a Flowmaster cat-back installed, so I was looking on performance opinions. I remember reading that they were pretty awful, but to the point where I should replace it? It sounds OK and the tips look decent.

Sell it and buy a Hooker cat-back with quad-tips? Thanks!

 

I had one on my stock ls1. Had it tuned with headers and all the free mods. Made 340 rwhp. After reading that they don't flow good, I took off the L tail pipe and looked inside.
I then made a longer tip for my Oxy/Act torch and cut away at the baffles.

In the end, it is just an open chamber. I did not have it re dynoed but by the seat of the pants, I could feel it come alive above 3500 rpm.

Now it's behind a 402 in my 01, and yes, it's a lil noisy on accell. Though I don't care, the sound is behind me

 

Its really hard to imagine that flowmaster does not perform well being that they have been around for a very long time. Pretty shocking.

 

Flowmaster is great for mustangs but suck big time for a f body,would you feel any gains by swwaping the flowmaster I doubt it,I didn't feel any change when I put my lm1 on my stock car,but with bigger mods cam,heads,etc I think it would hurt performance,overall they suck sell it and get something else

 

They sound pretty decent, I'm sure it sounds and flows better than stock. I would probably put the $$$ into an ls6 intake first and other things that would need replacing....shocks, endlinks, bushings, plugs, wires.....you see where I'm going

 

They only make +/- 5hp over a stock muffler. The "flow" is not good, but they sound ok with cats.

LOTS better CB options on the market.

 

Flowbastard
Blowmaster
Generally considered to be about the worst-flowing catback that you can get for an F-body, although it does sound good. You could always do what I did and put in a cutout for the track.

 

its not all flowmasters that blow nuts. just the f body 80 muffler that was not well designed. they sound good on a stock/light modded car and prob not really holding back much power. but start doing intake cam heads then they could hold ya back a good bit and they start to sound worse the more mods ya get into.

 

I have a 99 camaro and I have longtubes headers with flowmaster and you mean to tell me they are worthless? What's the best sounding mufflers? a nice but not too loud rumble

 

magnaflow, hooker, in that order...

 

Sell it and buy a magnaflow.

 

magnaflow for sure. Had them on my 2000 z28 before I put true duals on it. They sound even better with long tubes. Not stupid loud in the car and have an awesome sound when u hit throttle. If I get another Camaro that's the exhaust I'm putting back on it

 

I wasnt really happy with my magnaflow man. I know its popular on hear, but for sound wise i didnt really care much for it. My magnaflow didnt get louder as it broke in like some people say.

I would definitely take hooker catback over magnaflow. I would go Duals,Hooker then magnaflow.

 

If you want something loud go SLP LM1 no cats.

 

On a stock/bolt on car you are not going to notice a difference. I would get a set of long tube headers and if you like how the fm sounds keep it. If you want it quiet get a magnaflow, if you want it loud look into a lm1 or lm2.

 

Meh. I was driving around today and the Flowmaster seems to have some vbrations and rattles at certain RPMs. I had a DynoMouth on my last LS1 F-body, but that was pretty loud. I think I'll try a Hooker if I replace it...

 

when my car was bolt-ons only the flowmaster robbed about 12hp and 20 ft/lb of torque on the dyno with the cutout open and closed

 

Check my sig for numbers thru the cutout and my flowmaster catback.

 

If you want good muscle car sound, go w/ Magnaflow. If you want it to sound raspy and like most ricers then go with the LM1 or 2.

 

lm's are not that bad on a stock engine with a catted y. with heads/cam is raspy as hell