Basically this is how it goes-
(Ranked from loudest to quietest)
10 series - single chamber exhaust. Loudest of the flowmasters.
(actaully a racing muffler)
40 series- dual chamber exhaust. Next loudest. Very powerful,
aggressive sound. (My personal favorite)
80 series- extremely aggressive sound. (Designed for crossflow
applications ie- Camaros and Corvettes)
30 series- deep, powerful sound
50 series- somewhat deep- kinda mellow
70 series- very mellow- alot like stock exhaust
60 series- a 4 cylinder rice muffler
Delta flow mufflers- Most series offer original (described) mufflers and
delta flow mufflers. Delta flow mufflers are three chamber
mufflers. They are quieter than the original series. They have less
interior resonance.
I hope this helps Matt. If you have any more questions just post them and I will check back later. Also, I recommend checking out the flowmaster site (
www.flowmastermufflers.com). They describe every series in detail and provide sound clips. When I first started looking I was confused too. Good luck!!