m/cyl ID help

[Jeff S.]

I have a Delco m/cyl, casting number 5460346. It has 1-1/8" bore & the aft piston hole depth is approximately 1.6". The characters 2067 are stamped lightly on the machined boss between the front bleeder and front output port. The characters MK (or, maybe HK) are stamped on the front, semi-circular machined pad.

Am I correct to interpret this as a '72 model year assembly, with a Julian date of the 67th day?

Is the ~1.6" piston hole depth considered "deep" or "shallow" configuration?

Would this be a pwr brake application, or standard/unassisted brakes? (Perhaps there's no difference, as in '67?)

Thanks in advance.

[Terry M.]

Re: m/cyl ID help

Jeff,
Your date code work seems correct.

I am working from memory, and you really need the TIM&JG or someone with a better memory than I have. The manual brake casting number ends in 509. I can't remember the power brake casting number, but there is some controversy (I at first chose another more earthy expression, but thought better of it) about one of the numbers being a 6 or an 8. The sellers of the repop units have one number and the TIM&JG has another.

I know nothing about those measurements, but stand by. There are others who will jump in -- I am sure.

[Joe L.]

Re: m/cyl ID help

I have a Delco m/cyl, casting number 5460346. It has 1-1/8" bore & the aft piston hole depth is approximately 1.6". The characters 2067 are stamped lightly on the machined boss between the front bleeder and front output port. The characters MK (or, maybe HK) are stamped on the front, semi-circular machined pad.

Am I correct to interpret this as a '72 model year assembly, with a Julian date of the 67th day?

Is the ~1.6" piston hole depth considered "deep" or "shallow" configuration?

Would this be a pwr brake application, or standard/unassisted brakes? (Perhaps there's no difference, as in '67?)

Thanks in advance.

Jeff------


GM casting #5460346 is a 1-1/8" bore master cylinder casting used for 1967-76+ Corvettes with J-50 power brakes (for 1967 it was used only for J-56 but thereafter for both J-50 and J-56)). The date code on the one you have indicates the master cylinder was manufactured on the 67th day of 1972.

While the 5460346 casting was used for master cylinders used on other Chevrolet models besides Corvette, the "MK" broadcast code indicates this particular unit was a Corvette unit. The "MK" code was first used for later 1972 Corvettes with J-50 or J-56 power brakes. It was NOT used for any non-power applications.

The piston pushrod hole depth you describe is a "deep" configuration.

[Jeff S.]

Re: m/cyl ID help

Thank you, Joe. That clears it up for me.