C-3 Master cylinder

[John D.]

I am rebuilding my master cylinder on my early 68. It is the proper casting # 5455509 for standard brakes and has the two bleeders above the two lines. I have no reason to believe it is not the original. The flat on the front has a ZC code (Judging manual says it should be DC). The # on the flat next to the front line is 1314 is this the date?

It also has the proportioning block below the MC with some type of an electrical connection. Anyone got any ideas??

Thanks, John

[Harmon C.]

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[Joe L.]

Re: C-3 Master cylinder

Lyle and John-----

For these master cylinder date stampings the year is usually represented by the first character of the 4 numerals. So, in this case, the date would be the 314th day of 1971, or November 20, 1971, a Wednesday.

The '509' casting master cylinder was used for more than 1 finished master cylinder ASSEMBLY. The "ZC" code was not used on Corvettes, but I don't know what it was used for. The master cylinder MAY still be usuable for a Corvette providing that the internal parts are of the Corvette configuration. If the casting used for the "ZC" assembly was somehow machined differently than the "DC" casting was machined, then the master cylinder may not be usable for the Corvette application. It's very hard to say.

The block below the master cylinder is NOT a proportioning valve. It's a brake fluid distribution block and pressure differential sensing switch. The wire is part of the pressure differential sensing function of the piece. Proportioning valves were used only on 65-68 Corvettes with J-56 (adjustable type) and 78-82 Corvettes (non-adjustable type).