77vetteLS1

Hello, I'm in the process of overhauling my entire 77.. I have a questions regarding brakes, I purchased hydraboost, wilwood master cylinder, and wilwood six piston calipers front and rear.. What do I need to do in between the master cyl and the calipers? Should I run my stock distribution block or should I put in a proportioning valve. If I'm not mistaken, I thought the two reservoirs in the wilwood master where proportioned for front and rear brakes.. I don't have the mc yet, so I can't confirm this..

So, what should I do? Put in a proportioning valve or run the stock distribution block?

dannyman

Aside from the replacement of the listed components; re-install the complete system as per original set-up. Distribution blocks are necessary to get the brake fluid to the individual calipers. The proportioning valve is a safety item to identify when you have a brake system malfunction.

These components left in the system will not compromise the braking system. There is no advantage to removing them.

toddalin

A proportioning valve is to balance the front and rear brakes so that they lock up at about the same time. It can be used to compensate for changes in the brake system, vehicle weight, weight distribution (even from the presence/absence of fuel in the tank), wheel/tire combinations, etc., or just to optimize what you have. Remember that even though Corvettes came with different options' combinations that affect weight and its distribution (e.g., BB vs SB), they proportioned the brakes the same on most all of them.

I put one on my '64 on the rear brakes when I added front disks. If I didn't add the proportioning valve (and at first I didn't so I speak from experience), the rears would lock up way before the fronts would take hold and braking was terrible.

The valve lets me reduce the pressure to the rear brakes delaying this lock up so all brakes lock up at about the same time. I have mine mounted under the dash and can adjust it while I drive.

A proportioning valve is used to optimize the brake system and GM even installed adjustable proportioning valves on at least one of the Corvette brake options.

Mike Ward

You've got that a little backwards. The 'safety' aspect is a primary function of the simple distribution blocks. Ironically they only warn after you've discovered that you've lost brakes, not before.

Whether one is needed or not depends on the characteristics of the new master cylinder bore and piston. If identical to a stock master, leave well enough alone.

77vetteLS1

Thanks for the the replies.. So, if I understand, I should hook my new Master Cylinder up to the existing distribution block???

dannyman

This system really is not that complicated. I guess it's back to basics.

The '77 really doesn't have a proportioning valve; it's actually a proportioning/combination valve. The electrical component of this valve illuminates a brake warning light on the dash to indicate that the internal sleeve has been hydraulically shifted to one side or the other, as a result of a hydraulic leak in either the front or the rear braking system. When shifted internally it provides the ground to the electrical to activate the dash warning light. Alas, a safety device to indicate a brake system malfunction. You still have braking available at this time!

The purpose of the distribution blocks is , as the name implies to distribute the pressure from a single line to two lines; hence distribute. If you didn't have distribution blocks you would need addition lines individually from each caliper to the master cylinder. You now have a single line from the front of the master cylinder that flows through the proportioning/combination valve then a the single line to a distribution block which has two line outputs; one line to each front caliper.

Mike; The distribution blocks have no system safety aspects,what-so-ever!

To the OP, I would leave the original set-up. From the master cylinder it flows to the proportioning/combination valve; then individually one line forward to the front distribution block, as well as one line back to the rear distribution block, and from these blocks to the calipers.

dannyman

77vetteLS1; you did buy the tandem master cylinder with two reservoirs, right?

Mike Ward

The proportioning valve even less so; you brought the word into discussion, not me.

TheSkunkWorks

If you intend on actually putting those bits to their intended use, IMCO you'll need to add an adjustable prop valve so you can fine tune the brake bias.

gkull

Hook it in to the existing stock D block.

Then you have to test the system. weight, tires traction front to rear, pad type all come into play to balance the system

The six piston has less SQ. inches than my Wilwood 4 piston. I use the P-20 pads up front.

What diameter rotors do you have?

dannyman

The thread title and the actual question brought the word into discussion, not you nor I?


My comments were made to clarify the fact that the proportioning/combination valve, located immediately downstream of the master cylinder, provides a warning light to the driver (via dash warning light) that there is a problem with the brake pressure in either the front or rear portion of the brake system.

The concern was raised to make aware that this component serves a safety function, which should be left in the system regardless of other component change-outs or system modifications.