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  1. #1

    Default Exhaust Manifold Interchange

    I currently have my '80 mustang (3.3) at a repair shop and I'm trying to get some issues with the exhaust sorted out. I had a new muffler put on a little over a week ago and it made a huge difference in the gas mileage. It jumped from 13.3 to 19.2! The muffler looked good on the outside but was shot on the inside. Baffles were loose and a lot of rust fell out of it. I guess it was building up back pressure. Anyway, I brought it back to them to have them look at the rest of the exhaust. It sounded like it had leaks and made a puttering noise under acceleration. We thought that there was some kind of donut gasket on the exhaust manifold that was leaking. It took a lot of effort to get the nuts off as they were reluctant to let go after being on there for 38 years, but they finally did. Much to everyone's surprise, there was no gasket and the part that bolts up to the manifold is some sort of emissions piece, perhaps a catalytic converter of sorts. Not sure what you'd call it. It's shaped like a small pot and there's a wire mesh screen on top of it. I think finding one of these will be next to impossible and even finding a direct fit replacement for the for the other cat won't be easy or cheap. They said if I could find a different manifold for it, say from an older Mustang with a six cylinder engine, they could bend a new pipe for it and eliminate the cats entirely. I told them as long as the car ran all right I was fine with it. I have a six cylinder manifold from a '68 and I'm wondering if anyone can tell me if it would fit on my '80. We have no emissions testing here and I know removing them isn't the greenest thing to do, but I'm getting desperate to figure out a solution for this problem. They've had the car nearly a week and I'd like to get it back. I was driving my '66 Mustang, but the radiator decided to spring a leak, so now I've got that to deal with as well. Had to borrow my friend's pickup so I can get to work.

    If anyone can advise me on the exhaust, please let me know. I need to make a decision about what to do with it very soon, ideally sometime tomorrow morning.
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  2. #2
    FEP Senior Member
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    There probably wasn't a gasket there ever. That "thing" is a catalytic converter as is that boxy looking thing in the third picture. Is there any reason they cannot put the primary converter back on? It looks like it is mechanically in good shape.

    It looks like you have one of these:
    https://www.ebay.com/itm/80-81-82-GR....c100005.m1851

    Sorry, I don't know enough about the Ford straight sixes to comment on interchange. FWIW the exhaust manifold gasket has applications going back to 1960. I did find this from a similar vintage Mustang 3.3 that has a more conventional looking flange on it.
    https://www.ebay.com/itm/1979-1982-F...QAAOSwcxVapDuf
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  3. #3

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    Thanks. I appreciate the information. From what the shop told me, they shined a light inside them and they appeared to have carbon buildup as to be expected, although I think everything is still usable. After comparing the '68 manifold I have to the one you supplied pics of from eBay with the D7 part number, they appear to be exactly the same. I'm going to take it to the shop and tell them that if it will work, go ahead and put it on, bend a new pipe for it and eliminate the cats. If it doesn't work for some reason, I'm going to tell them to just put it back together as it was and hope for the best. The labor for this job is going to be expensive, but considering what the shop went through to get it apart, I'm glad I didn't attempt it myself. Knowing what I know now, I would have just left it alone and lived with the noise. I thought I was doing the right thing trying to fix it. If the cats are removed, maybe it will run better anyway.

  4. #4
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    it is hard to see the innards of the tea pot converter, but they might be able to hollow it out if it was plugged up. It sounds like the '68 manifold might work just fine. Does your car have an air pump to run air into the exhaust manifold? Whatever you wind up doing be sure to post a follow up so if someone has the same issue later they can learn from your experience.

    Quote Originally Posted by Scott K View Post
    Knowing what I know now, I would have just left it alone and lived with the noise. I thought I was doing the right thing trying to fix it. If the cats are removed, maybe it will run better anyway.
    That is how is usually goes. You go in with the intention of fixing something that isn't a major problem and the whole thing just blows up in your face.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  5. #5
    FEP Senior Member
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    Any luck with this?
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  6. #6

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    The manifold I was going to try wouldn't work. There is a tube for the emissions that screws onto the manifold that's on the car and the one I was going to use doesn't have that fitting. Found one on eBay, but it was $140 and part of the tube is still attached to it, so there's probably a reason why they cut the tube off instead of removing it, like it was rusted in place. I just told the shop to put it back together and seal it up the best that they could. They put some kind of sealer on the flange and it was quieter at first, but burned off within 50 miles. Whatever it was that they used, it wasn't rated for that much heat. A friend of mine suggested trying to put some header wrap around the flange. May not work, but I don't think it will hurt to try. I'm just trying to find someone around here that has a partial roll or a small piece of the stuff. The rolls in the store are huge, much more than I would ever begin to need and are also around $50. The good news is that I went out this past weekend and bought a little Mazda 2 to drive to work, so now I can take my time getting the rest of the issues on the '80 sorted out. Gas prices are climbing around here, so I think this decision was well timed. The air isn't working in the '80 yet either and the temps here are going to be in the upper '80s in the next couple days, so again, getting this car was well timed. I have to take my dad places sometimes and he's 92, so good A/C is important. I'm just going to keep chipping away at the rest of the mechanical issues on the car until they're done. Fortunately, there's not a lot left to do to it.

  7. #7
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    I am sure that tube and fitting from the ebay manifold could be removed. A lot of times people just cut the tube off because it is faster and easier than removing the fitting themselves. I am also sure I probably wouldn't give $140 (+$20 shipping) for a stock six cylinder exhaust manifold. I'm not sure what the application difference is between your car and the regular flange manifold. If you could figure that out it would help in the search for a new manifold.

    This guy is selling one for $40 (assuming the listing is still active). Do note that is has two Thermactor (or whatever Ford called it) ports. One on the end and one by the collector. Not sure how many your current manifold has.

    http://www.borthautoparts.com/images/cars/ford/Exhaust%20Manifolds%20Ford%20%20Mercury%20Misc%20Y ears/1977%20Ford%20200,250%20Mustang%20Exhaust%20Manifo ld%20No.D7BE-9430-CA%20$40.00.JPG

    http://www.borthautoparts.com/make/f...0Misc%20Years/
    Last edited by KevinVarnes; 05-09-2018 at 10:46 PM.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  8. #8
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    I used to have (sold it all off) a tubular factory-type header from a 1995 Ranger that I used. I just went and ordered a high-flow cat and had the exhaust shop do the rest (as they wouldn't construct the after-header tubing without a cat due to legal reasons). It woke the car up and made a much better sound to boot. Sold the car a short time later to fund one of the other projects I have/had going.
    " If you're not living life on the edge, that means you're taking up too much room."
    1979 Mustang Indy Pace 2.3T/4spd (sold on 1/10/16)
    1983 GLX vert 3.8/auto (triple black, sold on 10/8/13)
    1984 (early) Turbo GT (parts SLOWLY coming together)
    1985 Coupe 4.6L DOHC/IRS swapped (sold 9/10/17)
    1986 GT TTop 5spd (sold as of 10/8/13)
    1988 Thunderbird TurboCoupe (Cobra IRS/Brakes/big turbo project)

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