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2.5" OR 3" MUFFLER ????

Discussion in 'The Garage' started by tuner-automotive, Jul 12, 2005.

  1. tuner-automotive

    tuner-automotive Registered Member

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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.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I've got a high flow cat and Borla 16" x 3" sportsman muffler. Sounds smooth and strong and goes well!
     
  3. trailblazr81

    trailblazr81 1/2 ton status

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    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.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    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.
     
  5. captaininsano

    captaininsano 1/2 ton status

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    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.
     
  6. trailblazr81

    trailblazr81 1/2 ton status

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    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.
     
  7. Mad-Dog

    Mad-Dog 1/2 ton status

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    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
     
  8. Mad-Dog

    Mad-Dog 1/2 ton status

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    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)
     
  9. tuner-automotive

    tuner-automotive Registered Member

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    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.
     
  10. trailblazr81

    trailblazr81 1/2 ton status

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    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:
     
  11. tuner-automotive

    tuner-automotive Registered Member

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    The cheapo is whats killin me................ thats what I thought.
     
  12. Mad-Dog

    Mad-Dog 1/2 ton status

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    I second that, a lot of aftrmarket mufflers are designed to produce that (sound) with little regard to flow characteristics.
     
  13. trailblazr81

    trailblazr81 1/2 ton status

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    Also depending on the mileage on yer truck you might wanna check the cat.
     
  14. tuner-automotive

    tuner-automotive Registered Member

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    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.
    [​IMG]

    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.?
     
  15. Mad-Dog

    Mad-Dog 1/2 ton status

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  16. tuner-automotive

    tuner-automotive Registered Member

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    Mad-Dog, thanx but the link no worky.
     
  17. Mad-Dog

    Mad-Dog 1/2 ton status

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    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
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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  19. Thunder

    Thunder 3/4 ton status

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    One litlte word...........3"
     
  20. Mad-Dog

    Mad-Dog 1/2 ton status

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    Thanx for fixing that link bro..... :wink1:
     

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