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  1. #1

    Default Exhaust Pipe Size coming out of Long Tube Headers

    Hey Everyone- I'm putting some long tube headers on my 2005 1500 Sierra w/ the 5.3. I've been doing some research and found that most people suggest going with a 2.5" pipe for true duel exhaust. With that said the stock diameter coming out of the stock manifolds is 2.75". Would I lose much by running 3" pipes from the header to a magnaflow 2 in (3") 2 out (2.5") muffler? Or should I reduce the pipe size to 2.5" right out of the headers and just go with the muffler being all 2.5" ins and outs? Just figured I'd get a little more input before purchasing the muffler. Thanks

  2. #2

    Default header to muffs question

    sorry is this is a double post...Keeping in mind that your truck is essentially stock, there won't be any problems reducing to 2.5" coming off the headers. You are running two pipes into the muff, and two out, so I can't imagine there being any backpressure issues. Running 3" pipes into the 2.5" muff will be the same as running 2.5 all the way. Since you are using a Magnaflow muff, I am sure their tech line would be glad to take your call with any questions. Jim
    Las Vegas, NV...2001 Silverado 1500 LT Z71 Stepside X-cab, 171,000 miles, 5.3, cat-back duals, leveling kit, 3.73, 17" rims, more to come...

  3. #3


    That is plenty... most performance exhausts such as corsa using a single inlet dual exit exhaust run a 3" pipe up front with 2 1/4-1/2" tailpipes. Is there a reason you do not want to run a x-over pipe? Doing so will make it easier to tune as it provides for a more equal/consistent back pressure for all cylinders. Just something to consider.

    Sorry I didn't catch the dual in dual out muffler... this accomplishes the same thing as a x-over pipe. Guess this is the downside of using my phone to access the forum.
    2009 Chevy Silverado 2500HDLT 6.0L w/ Towing Package, Dick Cepek GM8 Rims, Dick Cepek FC II 33X11.50R17,RKSport Ram-Air Hood(Functional), Lazer Lite Aluminum Tonneau Cover, Road Armor Stealth Bumper, PIAA Lighting, Diablo Trinity Tuner, Diablew Custom Tune, BullyDog Cold Air Intake, American Racing Headers w/highflow cats, Corsa Performance Sport Exhaust, Custom Striping, Black Bowties front and rear, Fuel Grille Inserts, Recon Headlights, Readylift Shocks, Readylift Upper Contol Arms, 2" Blocks in the Rear..

    Future Plans: HD Tie Rods, Under hood upgrades, Crower Camshaft and possibly electric fans.

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