[Ed Sellers]

Hello" I have a 65 gto with manual brakes, changing to original master,the master we took off has a 1/4 dimple on the piston, the original I had rebuilt came back with a deep hole in the piston. My rod won't work with the original master. Can some one please tell me which one is correct. Thank you.

[RAII 4-speed]

I actually have an NOS one I can look at and send or post pics if you wish...or...can you post pics of yours?

[Ed Sellers]

Hello Ra11 4-speed, do you have a nos master cylinder, can you send me pics I can't send pics on this I pad, but if you give me your e mail address I can send you pics from my phone. Thank you.

[John62]

There are two rod sizes, go to any vendor like ames or inline tube you will see a long and short. Long for the deep hole master and short for the other.

[goatman65]

I think one is manual the other power brakes.

[Zimtok]

Originally Posted by goatman65

I think one is manual the other power brakes.

YES...
If I remember correctly:
The shallow hole is for power brake booster.
The deeper hole is for manual brakes, the deeper hole helps keep the shaft in place.


.

[Tom Vaught]

Originally Posted by Zimtok

YES...
If I remember correctly:
The shallow hole is for power brake booster.
The deeper hole is for manual brakes, the deeper hole helps keep the shaft in place.

.

(Additional Comment) the 64 Manual Brake master actually had a Push Rod retention device built into the Master Cylinder design. Not sure about the 65.

Tom V.

[Tom Wood 64]

Ed, 64 and 65 masters are the same for manual brakes. I have looked at 5 plungers I have and they all have about a 1/4 inch dimple. If yours is deeper then that, at NAPA ask for united #432 master rebuild kit and switch plungers. If you just switched masters and nothing else this should fix your problem.

[Tom Wood 64]

As far as the two rod sizes, that is from power booster to master depending on application. Clevis rods are all the same size but pinned in different locations on brake pedal arm depending on manual or power brakes. Upper hole manual. Lower hole power.

[John62]

Originally Posted by Zimtok

YES...
If I remember correctly:
The shallow hole is for power brake booster.
The deeper hole is for manual brakes, the deeper hole helps keep the shaft in place.


.

Are you sure about that or does it depend on the year. My 65 came with power brakes and appears to have the original booster on it, It had the long rod so the master had the deep hole and the brakes worked great. I decided to install the 67 duel set up, I got the kit from Inline tube using my original booster and they gave me a master with a shallow hole and sent me the short rod. Haven't tried it yet, I wonder if it will work?

[Tom Vaught]

It should work fine because the short rod will be 'trapped' between the master and the Power Brake unit.

64 Master cylinder pushrods were 'retained' by a special retainer (at least on the 64 KC built manual brake cars).

The rod from the pedal should be able to be used in either configuration just the rod needs to be moved to the lower hole to have less pedal travel/mechanical advantage when used with the power brake parts.

Tom Vaught

[Ed Sellers]

Originally Posted by Tom Wood 64

Ed, 64 and 65 masters are the same for manual brakes. I have looked at 5 plungers I have and they all have about a 1/4 inch dimple. If yours is deeper then that, at NAPA ask for united #432 master rebuild kit and switch plungers. If you just switched masters and nothing else this should fix your problem.

thanks for the info Tom wood 64, I found a original master cylinder core in excellent condition, just got it back from rebuilding it has the 1/4 dimple piston. The deep hole piston is for power brakes. Thanks much.