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2.5" exhaust pipe to manifold adaptors

Discussion in '1982-Present GM Diesel' started by 6.2Blazer, Jan 28, 2004.

  1. 6.2Blazer

    6.2Blazer 1/2 ton status

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    2.5\" exhaust pipe to manifold adaptors

    My old 2.25" mufflers are rotted out and I found a good deal on a set of 2.5" 40-series Flows. The local muffler shop says they probably can't attach 2.5" pipes directly to the factory manifolds. I seem to remember some discussion about a person making adaptors to allow this, but did a search and can't find it. Anybody have any information on this?

    What about Hummer headers? Are they a diret bolt-on .......or worth it?
     
  2. TK5

    TK5 1/2 ton status

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    Re: 2.5\" exhaust pipe to manifold adaptors

    I don't have anything to add, but my muffler shop grafted 3 " dual from manifolds back for me on my 6.2. I guess it has something to do with the amount of time the shop wants to spend on such a project. The shop worked on mine after shop hours. I guess it has something to do with this was a former student of mine that owns the shop.
     
  3. bigblock454

    bigblock454 Clack Clack Clack Premium Member

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    Re: 2.5\" exhaust pipe to manifold adaptors

    I don't remember what year but thedieselpage.com has an archive article on making those adaptors. They were built by Dr. Lee.
     
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: 2.5\" exhaust pipe to manifold adaptors

    The local place said they could start with a short section of 2.25" at the manifold and then adapt it to 2.5" further downstream. I just wanted to check out all of the options first.
     
  5. arveetek

    arveetek 1/2 ton status

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    Re: 2.5\" exhaust pipe to manifold adaptors

    I'm the guy that has those adapters. The adapters were first designed by Dr. Lee Swanger from The Diesel Page.

    The stock exhaust manifolds will only allow about an 1 7/8" pipe to clear the manifold studs. The factory exhaust starts with that small pipe coming out of the manifolds, then it turns and swells eventually into 2 1/4" pipes.

    What I did was removed the three manifold studs off of each manifold. If you measure the actual opening on the manifolds, they're almost 2 1/2". But, by the time you add one of those exhaust doughnuts and one of those large clamps designed to fit over the studs, you've got a fairly restricted pipe in there.

    My adapters bolt directly to the manifolds themselves, and the adapters have three drilled and tapped bolt holes which allow actual 2 1/2" collectors to be bolted directly to them. This means I have 2 1/2" pipes bolted directly to the manifolds. The narrowest passage in my whole exhaust system is the diamter of the outlets on the manifolds.

    I used some mandrel-bent pipe fittings I got out of JC Whitney and built my own custom exhaust system. It goes from 2 1/2" duals to 3" duals.

    If you're not in a hurry, I'll be removing my adapters later this spring when I install my turbo. I won't need them anymore, be happy to sell them to you pretty cheap. Or you could make your own. I had mine made at a machine shop. They charged my $75 to make them, but I think I could have gotten a better deal if I had shopped around. It was a pretty expensive shop.

    When I get done with my turbo install, I will have a 3" downpipe, followed by a 3 1/2" transition pipe, into a 4" muffler and tailpipe! I've already got a 4" muffler. That thing is huge! /forums/images/graemlins/thumb.gif

    Casey
     

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