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Thread: Might be getting a supercoupe I have a few questions.

  1. #1
    Join Date
    Jan 2003

    Might be getting a supercoupe I have a few questions.

    Ok In the next week or so I might be picking up a 1990 35th anny supercoupe (auto) with around 70,000 miles on it. I am wondering what the first things I should do to it are? I am going to give it a tune up of course (new spark plugs, filters, check plug wires, etc) but while I am in there I want to help with it's reliablity and performance. So I guess I want to know what kind of exhaust does everyone perfer to free up back-pressure and sound good? also are there any problems with the auto trannys in these? any preventitive maintenance i should to to the drive train? and what is the widest tire that will fit on the stock sc wheels?

  2. #2
    I agree with changing plugs, fuel filter, oil. Are you going to do this yourself??? Be prepared because the plugs are not easy the first time that you do them. Use Motorcraft Plugs and if you can afford spring for the Magnecore Wires because they are a perfect fit and great performing wires.

    AOD transmissions are notorious for failure. Mine went out at 94,000 miles and was rebuilt. I would consider changing out the tranny fluid and maybe adding a shift kit to improve shifting and help prolong the life of the tranny.

    The resonator is the single largest restrictor in the exhaust system. either replace it with a different resonator or have a straight pipe welded in. The mufflers are not too bad but you can do better. I have a straight pipe and two magnaflow SS mufflers and it sounds really good. I get comments on it quite often by even non Super Coupe owners. There are also some lips that can be ground down at the end of the exhaust manifolds on the inside to open them up some also. You will need a die grinder to do that.

    Remove the air silencer, get a larger MAF, and maybe a 5% or 10% pulley and you will notice quite an improvement in performance. The smaller pulley will be an improvement that you will be able to feel instantly.

    I have a 90SC that has a all of the above plus a 10% and a SC Performance CAI and it runs pretty good. I get a solid 15 lbs. of boost in the upper rpm range with no knocking.

    And BTW if the headgaskets have not been replaced that repair will always loom and may happen quicker once you start modifying the car. The boost is actually the amount of back pressure that is measured right before the air goes into the intake manifold. I can assure you that increasing the amount of boost does not help prolong the life of the headgaskets.

  3. #3
    Join Date
    Mar 2004
    Clarksville, TN
    as far as exhaust, if you want it to sound good, a resonator is pretty much a must. the stock one is pretty restrictive. you might also want to change out your cats for a set of high flows. if you even want or have to anyways. otherwise, just get a set of downtubes. as far as your tranny, get a shift kit for it and it'll vertainly extend the life of it for a good while. for the exhaust stuff, wynn at has great prices. for the shift kit i recommend bill at both are great guys to deal with. good luck with the car.

  4. #4
    Join Date
    Sep 2004
    Any kind of exhaust is better than stock. You can buy a complete exhaust system from SCP, the dynamax but it will cost you about $700 if i recall correctly. I just bought the 2 1/4" downtubes from texas thunderbirds in which they deleted the cats into two summit glasspacks and then Yed into single 3" exhaust for the mid-section, and Y pipe into 2.5" pipe that goes through Hooker Aerochamber mufflers. It sounds good, no crackling. Its quiet and smooth.
    As far as plugs and wires go i have the taylor 8mm wires. They are cheap and work great with the autolite double platinum plugs. plugs and wires arent that bad to change, I think the level of difficulty is skewed because it only took me an hour to change them by myself taking my absolute time.
    After those do an in fender intake with a cone filter and a pulley then see where it takes you from there
    1994 SC
    4.5L Twin Turbo SVO
    Project GTFD

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