Which is Correct for a 65 Riv GS (If either)

I have two master cylinders that came directly off 65 Riv GS's. The one on the left has a bleeder, the one on the right does not. (Please note fancy Buick workbench.)

1) Which is correct for a 65 Riv GS?

2) If one is incorrect, for what model is it correct?

3) if they are both incorrect, what is correct?

4) To whom do I eventually send one if it needs to be rebuilt?

 

What are the cast numbers ?
Does the one on the right have a bleeder vale on the side ?

 

The one on the right looks like in mine 66 Riv.

 

It all depends on the brakes, power or manual and the cast numbers.

 

The one with the bleeder:


The rusty one without the bleeder:

 

My 65 Riv GS and both parts cars had power drums.

 

Neither one is "correct". There were two brake suppliers to Buick in `65, Delco Moraine and Bendix. The pictured masters are the Delco Moraine style (but not correct for the `65) with the bail type lid. The Bendix style has the screw on cap. The original master cylinder did not have a bleeder and exited out the side. Your "rusty" master looks like the `63 style which had a hydraulic brake light switch mounted out of the front, but now has a plug.

Tom Mooney

P.S. The original Delco and Bendix style masters are not interchangeable due to the depth of the pushrod hole in the master piston.