My 69 brake cylinder is for power brakes, but I don�t have power!

[Steven B.]

[Joe L.]

My cylinder #5460346 (power brake master) is in my car but I don’t have power brakes-I’ve included the pic of the cylinder in case someone can see something that I don’t. The car is December ‘68. I assume maybe it was changed out over the years and this one was quickly available. I’m trying to get the small items that are not numbers matching to be correct, so I will be changing it out unless someone things either the power was removed or the wrong cylinder was installed incorrectly in ‘68? Any guidance is appreciated.

Steven------

I HIGHLY doubt that an incorrect master cylinder was installed at St. Louis. A master cylinder is part of the critical safety-related brake system and would require engineering approval for a substitute part (and, I HIGHLY doubt such engineering approval would ever be received). This incorrect master cylinder will affect pedal effort and pedal travel. However, aside from those issues it should work OK as it obviously has.

I would check the manufacturing date code to see if it's consistent with the car's build date. This can be found on the machined surface of the forward brake line boss. If the date code is inconsistent with the car's build date, then you know this master cylinder could not be original.

However, I can tell you right now that this master cylinder is NOT original to the car, even though it is a genuine GM master cylinder. Note that the master cylinder is not equipped with bleeder valves. All 1969 Corvette master cylinders, standard or power, were equipped with bleeder valves. Later in the C3 period the bleeder valves were deleted. I think you will find that the date code shows a later-manufactured master cylinder.

[Steven B.]

[Joe L.]

Thank you Joe, your advice and reasoning is second to none. The date code is CN 8297 so if the 8 was for '68 and the 297 was Julian, then it would work, but if the cylinder is wrong then it's still wrong, even though it works well. I will probably try and find a proper non-power cylinder that can be stamped correctly and make the change.
Much appreciated.

Steven-----


The "8" must refer to 1978. As I mentioned early C3 master cylinders were equipped with bleeder valves. Also, I believe the "CN" is a broadcast code. Earlier C3 master cylinders of this casting number carried a broadcast code of "PG" stamped on the "half-moon shaped" machined surface at the front of the master cylinder. I believe later power brake master cylinders had the broadcast code on the same surface as the date code.

[Steven B.]