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2.5" OR 3" MUFFLER ????

T

tuner-automotive

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So I have a 91 GMC Jimmy w/a 350 5.7l TBI and 700r4 tranny.
I run a TBI spacer / pod spacer / and 14" K&N filter with a flipped lid.

When I bought the truck it came with a 2.5" Ravin muffler.

All the other trucks I have had , all being 89 Chevy k1500 LWB PU , had 3" flowmaster mufflers.

If I put the 3" flowmaster in place of the 2.5 Ravin , will I loose torque?

Or should I just put another 2.5" flowmaster on in place of the Ravin.

The setup right now has the 2.5" ravin muffler flange spread open to fit around the 3" stock exhaust pipe.
 
I've got a high flow cat and Borla 16" x 3" sportsman muffler. Sounds smooth and strong and goes well!
 
If its 3" pipe I would say go with a 3" muffler. You shouldnt loose torque since you already run 3" pipe to the muffler.
 
Actually, a link to an article recently posted on this site, by David Vizard, concerning exhaust, as I understood it, said that if you are dealing with a restriction in the exhaust (such as a converter or muffler) a way to combat that is to increase the inlet/outlet size on the restriction.

Again, as I read it, that would mean a 3" muffler with 2.5" pipe, as a for instance.
 
Unless your 350 makes over 450hp you don't need it, and yes it will hurt torque in my experience. Big diameter exhaust is best suited for high rpm power. Dual 2.5 is the way to go.
 
captaininsano said:
Unless your 350 makes over 450hp you don't need it, and yes it will hurt torque in my experience. Big diameter exhaust is best suited for high rpm power. Dual 2.5 is the way to go.
Click to expand...


I believe he was talking single. I have a 383 pushing 450 HP with 3" duals. 5 years ago I had a 81 Blazer with a 383 making 350 HP and arount 450 lbs torque with headers going into single 3" pipe, hi flow cat, and 3" 40 series Flowmaster. I could have went dual 2.5" after cat but would have been spending money for looks and not HP or torque.
 
Actually dual 2.5" pipe is even too big for most engines and causes a loss of torque.
2-2.25" duals are adequate for most sytems........and yes, i would use a 3" muffler on a single-sytem with 2.5" pipe
 
what's bugging me is the way the Hooker Comp's fit it is darn near impossible for me to add collector length to the sytem, the collectors need to be about 15" longer to really boost the torque up some more (+ 30 ft lbs)
 
As far as HP #'s are , I have a stock longblock , other than the TBI mods I have done and the K&N.
Im running 33x12.5x15 APT tires and the current muffler installed (PO) is a Ravin 2.5" single outlet exhaust (autozone cheapy $28.50)

The stock pipe from the cat to the muffler is 3" .
The PO spread the inlet tube on the Ravin muffler to fit over the 3" aftercat pipe.

I guess Ill go with a 3" flowmaster , or even a 3" cheapy muffler as the stock pipe is already 3" outa the cat.
 
Its the cheapy muffler that killing you. A buddy of mine had cheap "turbo" performance mufflers and it really choked his motor. He went to a straight through design and the difference was night and day. So get a quality hi po muffler. :wink1:
 
I second that, a lot of aftrmarket mufflers are designed to produce that (sound) with little regard to flow characteristics.
 
Just rolled 170k yesterday.
I dont have any idea what kind of HP it puts out.

I have only had the rig for about 4 months.
normal_90%20Jimmy%20pass.JPG


But Ive done alot since I got it.
Heres a run down .

170,000 miles and runnin gooooood.

350 5.7L TBI
700r4
Stock front and rear gears(I think)
10 bolt frt and back
33x12.5x15 Super Sport
15x8 american racing wheels.
A/C
PWR eveything
14"x4" K&N filter w/flipped lid
TBI pod spacer
1" TBI spacer
NGK copper plugs
Stock plug wires
Drain and filled all fluids(oil, anti, frt and rear diff ,transf, tranny)
Seafoam treatment :waytogo:
New O2 sensor
New Fuel Filter
New frt brake pads

All thats left to do to my truck , for me , is the exhaust.
I just wanna get something on there thats gonna better perform with I have already done , as listed above.?
 
I'm sorry, my bad......

This is what i would do and is very similar to the system i have on my truck it's not the cheapest route but the best and works for any combination of parts that you put together.

1 5/8" Hedman Hedders with 3" collectors

3" pipe back to the rear of the transfer case, reduce to 2.5" pipe and install balance tube directly behind transfer case

2.5" back to a pair of HIGH-FLOW mufflers like Dynomax Super-turbo or Flowmasters, it is critical that you get mufflers that don't restrict exhaust flow as this will cost you power

Over the rear axle and out the sides at a 45 degree angle

If ya do it right the exhaust sytem can add significant amounts of HP.....!

Check out my web page for a pic of the exhaust, it's a little blurry but you can see what's goin on
 
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