65 power brake master cylinder

[Leroy Lemmerhirt]

I have a 65 with power brakes, does the original set up for J50(power brakes) have a proportioning valve? The AIM shows one but for j56(HD brakes) which I don't think was offered in '65? My car is an early '65 with 3/16 lines.

[Joe L.]

Re: 65 power brake master cylinder

Leroy-----

No proportioning valve was used for ANY 53-77 Corvette EXCEPT those 65-75 models equipped with J-56 HD power disc brakes.

[Jeremy Hedges]

Re: 65 power brake master cylinder

Joe, I don't think that that is right. I believe in '67 all corvettes had dual master cylinders with a proportioning valve.

[Joe L.]

Re: 65 power brake master cylinder

Jeremy-----

The only 1967 Corvettes that had a proportioning valve were those few equipped with J-56. The rest of the 67s (and all 68-77) had a brake distribution block and differential pressure sensing switch but this device is NOT a proportioning valve. In fact, all 65-75 Corvettes with J-56 also had the brake distribution block and pressure differential sensing switch in addition to the proportioning valve. Although I may have indicated/implied otherwise in my previous post on this subject, only 65-68 Corvettes with J-56 had the adjustable proportioning valve; 69-75 with J-56 did NOT have the proportioning valve.

1978-82 Corvettes had a COMBINATION VALVE. This device combined brake distribution, differential pressure sensing AND proportioning functions. However, the proportioning function was fixed and non-adjustable.

Very often, the brake distribution block and differential pressure sensing switch assemblies used for 67-77 Corvettes are called "proportioning valves". They are absolutely NOT proportioning valves, though, and they aren't even remotely related to proportioning valves. The use of that term with respect to these devices in a complete misnomer.

[Craig S.]

Re: 65 power brake master cylinder

Jeremy - I believe what you are calling a proportioning valve (under the MC) is actually a distribution block that includes s warning light switch to indicate that the front or rear circuit has failed and lost fluid. Unlike a proportioning valve which controls the degree of force, this is merely a safety related item to indicate which circuit failed....Craig

[Larry S.]

Re: 65 power brake master cylinder

Craig on the 65/66 power brake master cylender there is no low level warning light

[John H.]

Re: 65 power brake master cylinder

Larry -

The switch is just a spring-centered plunger that only senses a pressure differential between the front and rear hydraulic circuits (which can be caused by either fluid loss or air in the system).

[Larry S.]

Re: 65 power brake master cylinder

Is that on the master? I have 2 66 power brake master cylenders and neither one has an extra port or an electrical conection for this,All ine have are the ports for the brake lines them selfs,

Or is this on the proportioning valve? witch I do not have on my car

[Jeremy Hedges]

Re: 65 power brake master cylinder

Larry, do you want to sell one of your master cylinders?

[John H.]

Re: 65 power brake master cylinder

Larry -

The master cylinder only has the two ports for the front and rear lines. On a '66, the main lines connect directly to the master cylinder ports, with no distribution block/warning switch (that didn't start until 1967, and was a separate part connected to the master cylinder with short pipes).