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Know anything about mufflers?

Discussion in 'Off Topic' started by Bigfoot, Apr 25, 2011.

  1. Bigfoot

    Bigfoot Clack Co. OR Well-Known Member

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    I bought a 1970 Blazer with a 350 a while back, the exhaust has a crossover pipe leading into the single muffler and the pinch seam of that muffler was blown out. The blown muffler has a 2 1/2" input and a 2" output and tailpipe, from the parts catalogs it appears to be the original size. That tailpipe isn't mandrel bent either. Last week I installed a muffler that I had laying around, same overall size, 2 1/2" in, 2 1/4" out. I had to run into town so I drove it installed but not yet welded and it sounded great at first, after ten miles the walls of the muffler began vibrating VERY loudly at idle.:huh: I got the welding stuff, drove home and welded it on. Too bad I welded it all the way around because it's still VERY loud at idle, enough to startle the neighbors horse. It's fine above about 1500 rpm. It's not leaking, the muffler walls are vibrating, I can quiet it down by squeezing the muffler.

    Too much back pressure? Should I hack that 2" tailpipe off with it's restrictive bends? I almost went out today to drill a hole into the muffler to balance the pressure. :laugh:
     
  2. deadeye

    deadeye Albany,OR. Moderator Staff Member

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    Is it supposed to have a resonator before the muffler?
     
  3. BobSigP229R

    BobSigP229R Enumclaw, WA Member

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    I'd make it easy and get a flowmaster muffler increase the outlet size while im at it to 2.5 inches. Rockauto.com has good prices and so does summitracing.com, i ordered mine off summit.
     
  4. chainsaw

    chainsaw East side of Or. Active Member

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    i'm no muffler installer,but is it possible to put them on backwards?
     
  5. Bigfoot

    Bigfoot Clack Co. OR Well-Known Member

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    Doesn't look like it. This is all late 60s technology remember and the pipes all look stock. The parts book show 2" out of the muffler, can't believe they used a single 2" tailpipe for a 350 but apparently they did.
     
  6. Flash

    Flash Vancouver Member

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    The old muffler with split seam was probably due to back fire of raw fuel in muffler causing split seam. Running too rich, choke problem or bad anti backfire valve bad. The muffler you had sounds like the baffle on the inside has rusted loose from the welds if the muffler had been used before it probably had condensation on the inside. Mufflers tend to go bad from the inside out. Resonators that I know of usually go on last.
     
  7. Redcap

    Redcap Lewis County, WA Well-Known Member

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    Summit has knock-off Flowmasters for around $30 each, 2.5" offset in, 2.5" center out. I'd make it easy on myself and just buy one of those.
     
  8. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    Sometimes noise that reaches the inside of the vehicle is caused by a panel or part resonating with the vibrations coming through the walls of the muffler.

    Premium mufflers that are designed for minimum noise are often built from a sandwich like material. There is an inner wall, some sound deadening material, and an outer wall. Since everything is welded in place, you could install some Header Wrap or Heat Shield material and secure it in place with some large bands (giant hose clamps). Sound deadening material can also be added under the floor covering, especially the area directly around the muffler.

    Either that or replace it with a premium noise reducing muffler. Unless you like lots of noise avoid the "High Flow" types that are designed to add noise for the crowd that likes it.
     
  9. deadeye

    deadeye Albany,OR. Moderator Staff Member

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    Just get out on the road, get up to around 55mph, turn key off, pump gas pedal about 15 times , turn key back on.....problem solved.
     
  10. MA Duce

    MA Duce Central Oregon Well-Known Member

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    Woven or knitted??? Wool or cotton?
     
    mjbskwim and (deleted member) like this.
  11. Bigfoot

    Bigfoot Clack Co. OR Well-Known Member

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    I looked these up, nice. Those and the Flo-Pro V Force knockoffs. Anyplace where I can buy either of these locally?
     
  12. Redcap

    Redcap Lewis County, WA Well-Known Member

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    No clue. I bought mine from Summit Racing. Shipping will be about $10 and you can expect them in a couple days.
     
  13. sheepdip

    sheepdip Redland Well-Known Member

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    i work at a muffler shop in estacada, a full on set of exhaust from manifolds back up and over the axle will cost you arond $500.00 with flowmaster knockoff mufflers$750.00 with real flowmasters
     
  14. Redcap

    Redcap Lewis County, WA Well-Known Member

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    Ridiculous prices.
     
  15. swoop

    swoop Milwaukie, Oregon Well-Known Member

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    If you're trying to get by on the cheap, just go to your local muffler shop around mid-week and ask if you can look through the scrap box. People have new factory mufflers cut off for a set of flow masters ect. every day. I love those early blazers, so if was mine I would save up a little cash, can that cross over pipe system and put on a set of true duals from the headers back. The old girl will love ya for it, and repay you with more go and better MPG's. ;)
     
  16. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    My gramma used to knit them for us
     
  17. bobbyburns

    bobbyburns mountlake terrace wa New Member

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    do you have headers on it if so put 40 flow master if you have 2 in 2 out you can get a flow master that fits i would go 21/2 pipe i do this all day at Brody
     
  18. bobbyburns

    bobbyburns mountlake terrace wa New Member

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    any muffler place they keep def rent ones on stock
     
  19. MarkAd

    MarkAd Port Orchard Well-Known Member

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    i would skip the horseplay and go to Stans headers, have hime make the exhaust fro you/
     
  20. sheepdip

    sheepdip Redland Well-Known Member

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    all posters here make it sound very simple. having worked at a muffler shop for the last eight years i can tell you for fact that hooking up to existing exhaust systems can be a pain in the a$$. everybody that comes in says all you have to do in hook up to existing pipes. pipes are rotten, hangers are broken, inlet and outlet positions are different. suck it up and have all new done by profesionals, cough up the bucks and you will have a system that works and lasts for years