Disc/Disc proportioner?

[chevy_mike]

Originally Posted by GMCPaul

Distribution block, this block was used on all 67-70 trucks, with front drum / rear drum brakes. The block is bolted below the master cylinder and is not a proportioning valve as it does not modulate line pressure. If there is a loss of pressure in either the front or rear braking systems, it will activate the brake warning light in the dash. Since this block provides equal pressure to the front and rear brakes it is also great for 4 wheel disc applications.
These distribution blocks do not have residual pressure valves in them.
Residual Valves:
These valves are used in brake systems where the master cylinder is mounted lower than the calipers, typically under the floor. This is a check valve that keeps either 2lb (disc) or 10lb (drum) of pressure in the system to prevent the fluid from running back and overflowing the master cylinder. These valves should be mounted as close as possible to the master before the proportioning valve. These valves are not needed on firewall mounted master cylinders.
Thus the reason our distribution blocks did not require a residual pressure valve.
A alternative to using a distribution block is a disc/ disc prop valve which again applies equal pressure to both.
I was taught this by Inline Tube.
GMCPaul

This is great info. I am getting ready to do a 4 wheel disc conversion on my '68 and now I know I will keep my drum/drum valve and not change to something else. I will plum in a adjustable valve after the distribution valve on the rear line, just so I can tweak the rears.