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Thread: Problem with 1953 Ford F-100 with late 70's 351M and C6 trans

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    Default Problem with 1953 Ford F-100 with late 70's 351M and C6 trans

    First post to the forum. So hello everyone.

    I recently purchased a 1953 Ford F100 that has quite a few modifications made to it over the years. The one that is the most important right now is the 351 Modified engine and C6 transmission that was installed in it at some point. I have been tinkering on it to get it to run right but have run into a major problem that no one seems to be able to figure out.

    The problem is that when I'm driving the truck after the engine has warmed up, when I stop the truck, the engine starts to rev up and will not idle down until I put it in reverse or park. I can then put it back in drive and it's fine until I stop again. It only does this after the motor has reached operating temperature.

    The engine does have a few modifications to it. It has an aluminum Edelbrock intake and 600 CFM carb with electric choke. It has an old aftermarket HEI distributor vacuum advance with new wires and plugs. There is a booster/master cylinder hooked up to the vacuum and a vacuum line running to the C6 transmission.

    The only thing I can think of is something with the vacuum lines that could be causing the surge during idle. Has anyone else seen anything like this or have any suggestions? I do plan to unhook the vaccum line to the distributor this weekend to see if that makes any difference.

    I do live in Alexandria, VA for those in the area.

  2. #2
    THE GIFT! DaadyLong Legs H2_RECOVERY's Avatar
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    Does the trans have a vacuum modulator on it! If so plug the line at the modulator and see if it runs fine. If it does replace the modulator.

    Welcome aboard!!


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    Quote Originally Posted by H2_RECOVERY View Post
    Does the trans have a vacuum modulator on it! If so plug the line at the modulator and see if it runs fine. If it does replace the modulator.

    Welcome aboard!!


    Odd, I thought I would get an email when someone responded and never thought to check back. Thanks for responding H2Recovery and sorry for the very late response. I don't know what a vacuum modulator is, but I'll do some research on it.


    Since it has been quite a while since I posted, I have done quite a bit. The biggest thing was that I swapped the carb for an MSD EFI system in the middle of the year. That seemed to fix the high idle problem, but it has not fixed the problem with the trans staying in gear when I try to shift to neutral. It hasn't been enough of a problem for me to work on that any further. I have some other issues with the motor and realize that at some point I have to pull it and do a rebuild, or at least redo the heads. I believe I have a sticky valve when the engine reaches operating temperature.


    While it's not a 4wd, the '53 F-100 is a fun truck. I decided to go all in for the truck last month and ordered a TCI custom chassis that will modernize the whole suspension and drivetrain. I'm going to go with a chevy 350 SB with a 700R4 (or similar overdrive automatic). I have the engine already, but I haven't gotten the chassis yet. If anyone is in the Alexandria area and interested in learning or teaching a little about building up a truck from the frame up, I'd love to have the company.

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