1990 Brougham 5.7 dual exhaust
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 1990 Brougham 5.7 dual exhaust in Past Cadillac Vehicle Discussion; did some searching about dual exhaust and came up short. Eventually I'm going to do a 383 SBC, but I ...
  1. #1
    gntim is offline Cadillac Owners Member
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    1990 Brougham 5.7 dual exhaust

    did some searching about dual exhaust and came up short. Eventually I'm going to do a 383 SBC, but I need to replace what's there now. Are there any options short of a custom system? when I do the motor, what should I do for the front part, before the cat? I really don't want full length headers, maybe shortys. Thanks in advance!

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    csbuckn is online now Cadillac Owners Master
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    sven914 is offline Cadillac Owners Connoisseur
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    Re: 1990 Brougham 5.7 dual exhaust

    There are two ways of doing duel exhaust, without replacing the manifolds.

    The first option is to install a "Y" pipe coming out of the catalytic converter, and direct one side to the factory muffler and tailpipe and the other across the undercarriage, to and aftermarket muffler and tailpipe assembly. This is the most common method of simulating dual exhaust, and was used on mid-80's Broughams, equipped with the VIN 9 307 (Oldsmobile).

    The other option would be to cut a hole in the crossover pipe, which connects the right and a left exhaust manifold. You can then weld in a second exhaust pipe, with the catalytic converter, muffler, and tailpipe assembly. This method is more true to actual dual exhaust systems, except factory "true" dual exhaust systems don't have the crossover pipe.

    If you don't want to replace the pipe that goes over the rear axle, you can run a pipe out of the muffler, put a tailpipe tip on the end to make it flare out to the side, and have it kick-out before the rear wheel. I did this with my car, but I only have one exhaust pipe (I'm going to add a second one in the near future).

  5. #4
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Vin 9 broughams did not have dual exhaust...that was only on the 442s. All broughams had single exhaust pipes.

    If you don't want to hack into the crossover pipe, you can get a set of manifolds off an early 70s olds 350 powered car (98, 88, etc)-some of them did not have the crossover pipe.

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    Fleetwood472 is offline Cadillac Owners Fanatic
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    Re: 1990 Brougham 5.7 dual exhaust

    Check out this thread for some examples:

    http://www.cadillacforums.com/forums...st-design.html

    If you don't want to cut the crossmember you can buy a kit for I believe an 88 montecarlo. You will have to have it modified a bit for your application since your car is longer but it should bolt up. Basically it uses a 3 inch catalytic converter and then it splits to duals after the converter. It should work pretty well too.

  7. #6
    gntim is offline Cadillac Owners Member
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    Re: 1990 Brougham 5.7 dual exhaust

    it has a 350 Chevy in it now. I don't have to worry about emissions. I did find a little more info and someone said a g-body system from the cat back will work, not sure if thats true. Just looking for a cat back solution for now. I do have a 383 stroker that I will probably install someday, its not a 500 Caddy motor, but its paid for and the car is already set up for a chevy. Thanks so much for the advice.

  8. #7
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Quote Originally Posted by gntim
    it has a 350 Chevy in it now. I don't have to worry about emissions. I did find a little more info and someone said a g-body system from the cat back will work, not sure if thats true. Just looking for a cat back solution for now. I do have a 383 stroker that I will probably install someday, its not a 500 Caddy motor, but its paid for and the car is already set up for a chevy. Thanks so much for the advice.
    No worries about not putting a caddy motor in it....I have a chevy 350 (w/ long tube headers and an impala SS dual exhaust system) in my 86 FWB (formerly 307 olds powered)


    I believe the system for the late 80s monte ss and olds 442 will work as a cat back system (it will just have to be extended.)

  9. #8
    drmenard is offline Cadillac Owners Enthusiast
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    Re: 1990 Brougham 5.7 dual exhaust

    Correct me if I am wrong.. But could you just bolt on a 94-96 fleetwood exhaust system with the crossmember from that same 94-96 car? I think one thing I would do is use the 90-92 mufflers because of the hangers...and maybe just use a pipe and leave the cats off...

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    cadillac kevin's Avatar
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    Quote Originally Posted by drmenard
    Correct me if I am wrong.. But could you just bolt on a 94-96 fleetwood exhaust system with the crossmember from that same 94-96 car? I think one thing I would do is use the 90-92 mufflers because of the hangers...and maybe just use a pipe and leave the cats off...
    I'm not sure if the underside of the '90s would be the same as my 86, but with the late 80s ones, you'd have to weld up a support if you wanted to use the 94-96 crossmember (the factory passenger side crossmember support bracket (or whatever you call that piece that comes off the frame and supports the crossmember) is approx 6 inches too short)

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    Re: 1990 Brougham 5.7 dual exhaust

    Not sure if this will help you or not. Here is a universal CROSS-MEMBER TRANS MOUNT Kit I found on e-bay:
    http://www.ebay.com/itm/Build-yourse...082#vi-content

    I think sold by these guys......scroll down 1/3 of this page:
    http://www.transmissioncenter.net/gf...FQUFnQodQgEAUw

    These will give you the clearance to run duel exhausts.

    Regards,
    Chris

  12. #11
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Quote Originally Posted by cadchris
    Not sure if this will help you or not. Here is a universal CROSS-MEMBER TRANS MOUNT Kit I found on e-bay:
    http://www.ebay.com/itm/Build-yourse...082#vi-content

    I think sold by these guys......scroll down 1/3 of this page:
    http://www.transmissioncenter.net/gf...FQUFnQodQgEAUw

    These will give you the clearance to run duel exhausts.

    Regards,
    Chris
    That is an interesting idea but it is cheaper (at least when I got quotes, it was) to either add a bracket to the frame so the 94-96 crossmember can be used or have the factory crossmember that came with the car notched. However, if the 94-96 crossmember isn't easily available where you live and you are a "do it yourselfer", that would be a great way to go.

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    jayoldschool is offline GM RWD V8 addict
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    Re: 1990 Brougham 5.7 dual exhaust

    I've got at least one extra LT1 crossmember. I'll throw it under the 81. Someday. Cue Dave in 3...2...

  14. #13
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Quote Originally Posted by jayoldschool
    I've got at least one extra LT1 crossmember. I'll throw it under the 81. Someday. Cue Dave in 3...2...
    I've got an extra one too...if it ever comes time for the lesabre to get a new drivetrain, I'll have it.

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    cadchris's Avatar
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    Re: 1990 Brougham 5.7 dual exhaust

    Not to hi-jack your thread, but I have a 91 Brougham, and I want to do the same some day. I was told exactly what another member said to do, and notch out the orig. crossmember, and take the notch piece out, invert it and re-weld it in or make a filler out of larger exhaust pipe to re-weld it in.......something like that.... I just figured I'd go with a new universal crossmember and I remember seeing that one I posted above.

    Any other ideas of what would work for a 91 Brougham to install a true duel exhaust?

  16. #15
    The-Dullahan is offline Cadillac Owners Master
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    Re: 1990 Brougham 5.7 dual exhaust

    Quote Originally Posted by sven914 View Post
    used on mid-80's Broughams, equipped with the VIN 9 307 (Oldsmobile).

    Laaaaaaaaaaaaaaaaaaaaaaame. I never got a fake Dual Exhaust with my VIN 9 and I therefore call Shenanigans.

    These photos will be useful after I get to put my engine in my car though.

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