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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » how far should adjustable booster push rod stick out

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    3/08/2021 12:38 PM  #1

    67fbck73
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    From: Otter Lake michigan
    Registered: 9/10/2019
    Posts: 13

    how far should adjustable booster push rod stick out

    I have been redoing my pedal support bracket and trying to set up the brake pedal height where I want it, pretty sure   I got that all good now( I had made a custom spacer and it was way to thick) now apparently I did not set up the pushrod adjustment to the master cylinder depth correct at all. I believe I read on here it is supposed to be .01 clearance. The question I have is how far do you who have this conversion (1967 mustang  Bendix booster 2000 v6 master cylinder) have the pushrod threaded out. The overall length of the threaded portion is with the acorn looking nut is about 1 inch I have it threaded out with between 1/2" to 5/8"  inch of threads showing to get to the .01 clearance adjustment leaving about 1/4 inch of thread engaged in the pushrod. Is this ok?

     

    3/08/2021 7:04 PM  #2

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,260

    Re: how far should adjustable booster push rod stick out

    You want 0.001” minimum.  0.010” is the absolute max.  Shoot for less.

    My method includes no measuring.  Adjust the rod until it is too long and the master cylinder rocks on the rod. Then shorten the rod 1/2 turn at a time until it no longer rocks. You should feel the master cylinder flanges fit flat against the booster.  Then when you are pretty sure you have zero clearance, shorten it 1/2 turn more. It will be just right.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/08/2021 9:20 PM  #3

    67fbck73
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    From: Otter Lake michigan
    Registered: 9/10/2019
    Posts: 13

    Re: how far should adjustable booster push rod stick out

    Thanks for the help Steve.

    Is there a general amount of thread still threaded into the pushrod you like to see? I am a little apprehensive about the amount I have left in the pushrod. After further examination I probably got 3/8-7/16 of thread engagement once I have the clearance adjusted as you say.  Do you feel this is safe? I am positive this is the issue I was having as I thought I had this adjusted correctly in the car before but I did not have this adjuster threaded out anywhere near this far.

    Chris
     

       •Thread Starter
     

    3/10/2021 9:07 PM  #4

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: how far should adjustable booster push rod stick out

    General rule of thumb for any fastener is to have 1/2 the thread diameter as engaged threads.  So, for a 1/4” threaded stud, you need 1/8” of thread engagement.   For a 1/2” stud, you need 1/4” engagement.   


    Seems like booster output shaft adjustment is always my first question when excessive pedal travel comes up. and universally the reply is “yeah, it’s right”  and I always doubt it but...


    It you have 1/4” thread engagement, you are in good shape.

    Do not use this rule on wheel studs!!!

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/10/2021 9:35 PM  #5

    Chaplin
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    Registered: 3/14/2015
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    Re: how far should adjustable booster push rod stick out

    MS wrote:

    You want 0.001” minimum.  0.010” is the absolute max.  Shoot for less.

    My method includes no measuring.  Adjust the rod until it is too long and the master cylinder rocks on the rod. Then shorten the rod 1/2 turn at a time until it no longer rocks. You should feel the master cylinder flanges fit flat against the booster.  Then when you are pretty sure you have zero clearance, shorten it 1/2 turn more. It will be just right.

     
    I followed your method when I did mine and it worked well.

     

    3/10/2021 10:12 PM  #6

    Rudi
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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
    Posts: 3,975

    Re: how far should adjustable booster push rod stick out

    MS wrote:

    General rule of thumb for any fastener is to have 1/2 the thread diameter as engaged threads.  So, for a 1/4” threaded stud, you need 1/8” of thread engagement.   For a 1/2” stud, you need 1/4” engagement.
    It you have 1/4” thread engagement, you are in good shape.

    Do not use this rule on wheel studs!!!

     
    Should be 2 times the nominal diameter, fine threads can be 1 1/2 times.
    I would not drive a car that had 1/2 thread  diameter engagement on driveline or especially steering components.

    Last edited by Rudi (3/10/2021 10:13 PM)

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    3/10/2021 10:18 PM  #7

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,260

    Re: how far should adjustable booster push rod stick out

    Most threaded nuts are not as thick as the diameter they are threaded onto, but I do agree, Rudi, that more is better.

    If 2x was the rule, a nut for a 1/2” bolt would be 1” thick.  I have seen anything near that thick on a mustang.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/14/2021 11:10 AM  #8

    67fbck73
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    From: Otter Lake michigan
    Registered: 9/10/2019
    Posts: 13

    Re: how far should adjustable booster push rod stick out

    Thanks,
    Last time I did this in the car I was somehow way off on the measurement. This time everything was on the bench did what you said had it rocking on the pushrod.  I used calipers and gauge blocks to double check It. I will double check it in the car with before bolting the master down tight to look for movement of the master with someone pushing on the pedal a tiny bit by hand. This should workout good this time can't wait to drive it. I've been doing a tilt wheel column and a cpp steering box that is supposed to be 13.6:1  plus adding some 2004 mustang seast at the same time.  So wish me luck lol

    Chris 

       •Thread Starter
     

    3/14/2021 1:01 PM  #9

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,260

    Re: how far should adjustable booster push rod stick out

    Good luck, Chris.

    Forget all that measuring and just use my common sense method and it will be fine.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

     

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