hirdlej

iTrader: (31)

Anyone know how many CFM the stock silverado SI-SO muffler is capable of flowing? Does anyone have any hardcore proof that on a street performance 6.0L that an aftermarket muffler will really yield any gains over the stock muffler? I already have decided that the stock airbox will be more than sufficient for this build so I want proof that an aftermarket muffler is better than a stock one. I would tend to think that the exhaust velocity has slowed down enough by the time it reaches the muffler that going aftermarket wouldn't gain a guy but no more than 5-7RWHP? I already know that a 364 cubic inch motor with a VE of 85% spinning no more than 6500RPM's requires no more than 581 CFM of intake manifold/air intake flow. Meaning if the stock muffler can flow at least 600 CFM (which I see being an easy task) why would going aftermarket be a more intelligent decision? Please add your thoughts and tell me why I'm right or wrong.

sonoma43

iTrader: (1)

The way I see it is muffler's only gain you sound, not performance. Thats just how I feel. Some people will often tell you that they gain 10-15hp I laugh at them. Unless your running FI then typically I dont see anyone gain any power with just simply swapping muffler's.

hirdlej

iTrader: (31)

That's pretty much what I'm thinking. I'm trying to take a scientific approach to this and see if changing mufflers really makes a difference. I think it would be sweet to have stock sound but with the added performance. Headers I do know make a difference as I have plenty of experience with this and I've seen it time and time again with engine dynomometers. Headers only will improve an engine if it was designed for headers. I've seen personally a built Oldsmobile 455 gain only 5 flywheel horsepower from going from X&Y manifolds to long tube headers. At any rate, what are others opinions and why?

GMCtrk

iTrader: (27)

I didn't feel any difference at all going from stock to magnaflow 22"

regency

iTrader: (15)

my cousin went from a magnaflow with a 22" case to a magnaflow with a 14" case and gained power everywhere but i dont know how much. another cousin went from a flowmaster to the 22" case magnaflow and gain power too!!!

Phantom

iTrader: (16)

i was actually thinking of putting a stock muffler on my truck as it is beginning to attract a lot of attention. then put some cutouts in for when i want to be loud...imo after mufflers are for sound only...NA that is

chevyguy7802

iTrader: (3)

If I remember correctly somebody on here cut one open and it looked very restrictive.....

HotRodV6

iTrader: (6)

the stock muffler is junk, holds water and will rust out eventually. Not to mention they weight a ton. I replaced my stock muffler with a 2.5 in/out dynomax ultra flow and noticed alittle differance in performance and sound and also seen a small gain in MPG.

IMO its money well spent, but just the muffler, the guys that drop a grand on the corsa cat backs are just throwing money away. the factory pipes flow just fine.

Leroy_454

Im running a stock d-max muffler and tailpipe on mine. Not sure the flow benefit but it has a nice tone. The quiet exhaust keeps me out of trouble haha.

L7 Sierra

My first "mod to my truck was the Flowmaster Super 44 3", and I gained quite a bit of punch off the line. Although if left to rev up the stocker felt the same. I mostly did it for sound, and Flowmaster since I haven't installed one before.

I also got a 3 mpg increase in traffic driving, and almost 1 mpg in highway.