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Thread: 750 HP feels like throttle is sticking.

  1. #1

    Default 750 HP feels like throttle is sticking.

    New member here. I've been searching around at previous threads but cannot seem to find anyone that has had the same issue as mine.

    I have a ProForm 750 "Race" version. Vacuum secondaries, no choke. It is on a mild 440 (roughly 425-450 HP). I bought it off a buddy when he switched to a 6 pack setup on his 440. We did a rebuild on it and changed the power valve back to a 4.5.

    When you leave off idle, any amount of skinny pedal results in the feeling of the throttle sticking. I've done more incidental burnouts in the past 3 days than I have in the past 20 years. I have checked and double checked the throttle linkage, TV cable, etc., and there's no binding outside of the carb.

    I've adjusted the accelerator pump to .015" clearance at WOT with a feeler gauge. I put a stiffer secondary spring in thinking that maybe the secondaries were opening too soon. I've tried different carb spacers thinking that maybe the butterflies were catching. There's more than adequate throttle return spring pressure. I have not found any vacuum leaks either.

    If anyone has any ideas, I would be more than appreciative. My buddies & I are all scratching our heads. I've always ran Eddy's in the past so this is my first Holley. I've been reading the Holley tuning handbook, but I cannot seem to find this situation anywhere. Thank you in advance.

  2. #2
    Join Date
    Jan 2010
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    Brisbane, Australia
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    1,546

    Default

    Put some lithium grease on the pump cam to lever contact area.
    I've yet to find a throttle body that is correct out of the box.
    Most need throttle shaft recentering, plate adjustment.
    Can you reproduce this sticking with a driver in the garage, and one under the bonnet checking what the carb is doing? Gary
    Regards, Gary

  3. #3

    Default

    I haven't been able to reproduce this feeling of sticking at any other time. In the garage under no load, it will not do it. Driving at any time off-idle, it will not do it. It will literally only do it directly off-idle.

  4. #4
    Join Date
    Jan 2010
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    Default

    Quote Originally Posted by dcarstens440 View Post
    I haven't been able to reproduce this feeling of sticking at any other time. In the garage under no load, it will not do it. Driving at any time off-idle, it will not do it. It will literally only do it directly off-idle.
    You need to remove the carb, and check the throttle plate relationship to the bores. Do not touch the speed screws at all until you have looked at from underneath. Need to know how much the transfer slots are exposed by, should look like a square. Gary
    Regards, Gary

  5. #5

    Default

    I'll look at that today. I did notice when I removed the line for the vacuum advance, that there was fuel in the vacuum port. Not sure if that would be related or not.

  6. #6
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    Default

    Unrelated, some residue can occur, depends on a few variables.
    Regards, Gary

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