Advice
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Banned Scam/Spammer
Joined: Sep 2009
Posts: 132
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From: Usa
Advice
Got a brake booster for my 1969 vette it currently has manual brake the problem is the master cylinder push rod is missing can I use my original one or does someone have the correct one?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Master cylinders basically came in two forms: PB or Manual. What's the difference? The depth of the MC piston inside the bore, which can be seen and measured from the mounting flange to the piston. And sometimes the mounting flange itself was different.
To make things more complicated, the booster rod evidently came in different lengths over the years. AND, some were adjustable, some not. Confused yet? It gets worse.
The gap or distance between the MC piston and the booster rod is imperative to be the correct match for your app. And that gap should be, as I recall; 0.060.
Too loose and the brake pedal travel will be unacceptable.
Too tight and the pads will constantly be in contact with the rotors.
To check that important gap, a special tool is available to verify not only the MC piston but the booster rod. Try Google for that tool.
Another cheaper way is too place a small dab of Playdough between the two parts. Install the MC and just snug the mounting nuts. Remove the MC and check the thickness of the clay.
To make things more complicated, the booster rod evidently came in different lengths over the years. AND, some were adjustable, some not. Confused yet? It gets worse.
The gap or distance between the MC piston and the booster rod is imperative to be the correct match for your app. And that gap should be, as I recall; 0.060.
Too loose and the brake pedal travel will be unacceptable.
Too tight and the pads will constantly be in contact with the rotors.
To check that important gap, a special tool is available to verify not only the MC piston but the booster rod. Try Google for that tool.
Another cheaper way is too place a small dab of Playdough between the two parts. Install the MC and just snug the mounting nuts. Remove the MC and check the thickness of the clay.
Burning Brakes
Joined: Dec 2008
Posts: 971
Likes: 45
From: Middlesex NJ
You really can’t use the manual master on a booster.
The bore on the manual master is smaller and requires longer travel but that makes the pedal easier for manual brakes
The bore On the master for powered brakes is larger and requires less travel but much more pedal pressure thus the need for the booster.
You will also need to change the position of the clevis rod on the brake pedal arm to the lower hole and the brake pedal switch bracket to a power brake switch bracket.
You will also need to open up the hole in the firewall for the booster clevis boot and drill two new holes in the firewall support for the additional 2 bolts at the top of the booster as the manual master cylinder only uses two mounting bolts.
The bore on the manual master is smaller and requires longer travel but that makes the pedal easier for manual brakes
The bore On the master for powered brakes is larger and requires less travel but much more pedal pressure thus the need for the booster.
You will also need to change the position of the clevis rod on the brake pedal arm to the lower hole and the brake pedal switch bracket to a power brake switch bracket.
You will also need to open up the hole in the firewall for the booster clevis boot and drill two new holes in the firewall support for the additional 2 bolts at the top of the booster as the manual master cylinder only uses two mounting bolts.
