NVRLATE

I have the 40 series american thunder system on my car and it sounds great. I also couldn't believe how much louder it got once I installed my cam.

nonojoe66

i have the 80 series and it was somewhat loud when i just had a stock car with the cat back, and now with long tubes and no cat it is very loud

fireman

Mine was loud until I put headers on. Got real quiet after that.

camarofan101

I have a 95 Z28 with the 80 series muffler and no cat.And its loud but not loud enough,for me that is.But you take the cat off and it will be louder Thats what I done with mine.

Deckstripes

Put an LT4 knock sensor on it. The more agressive advance changes the exhaust tone, they get a little louder, especially under light throttle, like parking lots. Not alot, but a little. Good excuse to do it.

matLT1

Get rid of or hollow the converter. I did that after installing my flowmaster exhaust and the sound was night and day. Louder and more aggressive.

MPZ28

Ditch the cat...Get the magnaflow cat-back system. You will be extremely happy with the over abundant decibles it will produce. Magnaflow is the most abnoxious and best sounding exaust i know of besides Borla or spintech.

BTW: FLushmaster is the worst exaust ever for f-body's ( no offense)

2000LS1Z28

Bingo...That's exactly the words that my friend used to described how much louder his Flowmaster muffler got after ditching the cat for an offroad pipe on his LT1..."The difference was like night and day." And this was anywhere from idle to WOT.

Randy L

Geez...I guess you guys (or gals?) are itchin' for a noise violation ticket! I have a stock exhaust on my '97 LT1 with a Flowmaster 80 series muffler. It is about twice as loud as the stock system at idle and about 4 times louder on mid throttle accelerations. It's MUCH deeper and more agressive than the stock. From inside the car, at WOT, the sound almost seems softer, but I had my friend do several WOT passes while I stood on the street. The sound does NOT get softer, as it seems from inside, it still has that real nice deep tone.

In fact, when I had my Z with stock muffler, I had several ricers rev at me. Now with my 80's, I haven't gotten a single rev. The tone does present a real mean/agressive note. Granted it's not AS loud as others out there...but do you want to wake the neighborhood and get noise complaints...or attract attention from the cops?

I will admit that the newer full size trucks with the huge aftermarket exhausts are louder than the FM 80's.

I think those that don't hear a difference between the FM 80's and stock may be going deaf.

For those that think the 80's too soft, here's question. Do you think the Harley Davidson bikes, and other choppers, have a nice sound or do you think it's too loud?

I was driving beside a '67 Mustang that had headers and duals with what looked like FM 40's (exact same shape & color). We were cruising at about 45MPH, and that car was SOOOO loud that it was actually disturbing.

Compstall

The LT4 KM doesn't advance anything.

JP2005

ok on my t/a it had stock intake manifolds w/ no cat and the 3-inch pipe and that thing screamed at wot and was decently loud at throttle...

and p.s. you all are wrong the 80 series is a little louder on the exterior and and much louder on interior if you dont believe me here:

40: http://www.flowmastermufflers.com/cg...ml?id=rqSSyRrg

80: http://www.flowmastermufflers.com/cg...ml?id=rqSSyRrg

so know the facts please...before you make this man purchase a quiter muffler

Mystic97Z

if you want to make it louder, ditch the friggin flowmaster and put borla or slp on it.. i've never understood the flowmaster, it makes the wierdest sound at wot

JP2005

that is true they do sound very odd on ls1's but on lt1 it is probably one of the best sounding exhausts

nb96king

how about remove the muffler and y the pipe to two monza tips.

very loud when you get on it and mellow if you let off, i.e. a cops around, the idle is pretty tough sounding too.

2000LS1Z28

Well, I don't quite have that set up, but I do have the Flowtech cutout welded into the I-pipe right after the axle...Sounds VERY tough...So being overly loud/aggressive when I want isn't a problem...I just want my Flowmaster cat-back to be a little louder when I want to use my muffler, that's all...

Like I've said, I'm eventually going to replace the cat with an offroad pipe and weld on bigger slash cut tips (stockers are too small) when I get the chance and see if that makes enough of a difference for me...I think it will...

BTW, I know the Flowmaster isn't the best for performance (that's not why I bought it)...I got it super cheap and I've always liked the Flowmaster tone...When I need the most horsepower though, I'll always just use the open cutout instead...

Thanks to everyone for their helpful info and replies in this thread.