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Adjustable Proportioning Blocks With Brake Light Switch
Adjustable Proportioning Blocks With Brake Light Switch

Adjustable Proportioning Blocks With Brake Light Switch

Universal Fit, Aluminum, 3/8"-24 Outlet Fitting, 4.00" Overall Length, 1.00" Overall Width

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Adjustable Proportioning Blocks With Brake Light Switch
Adjustable Proportioning Blocks With Brake Light Switch
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Part # 91031358
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This adjustable proportioning block allows you to run lines from the master cylinder to the block and then to the appropriate wheels. What is neat about it is that it also contains the proportioning valve and brake light switch. This dramatically reduces the amount of fittings needed and potential leaks.

The adjustable proportioning valve regulates rear brake pressure, helping to maintain correct brake bias between front and rear brakes. It is designed for dual bowl master cylinders. The distribution block connects to the master cylinder and distributes brake fluid to all four wheels. An easy to turn handle with directional arrows makes it simple to either increase or decrease rear brake pressure.

The block accepts 3/16" brake lines and the inlets and outlets on this unit are 3/8"-24 inverted flare females.  It has two inlets from the master cylinder, two outlets to the front brakes and one outlet to the rear brakes.  It includes five stainless steel 3/16" fittings and wiring pigtail for rear brake light switch. Mounts to any convenient location. This is not a direct factory replacement for original blocks. Some line modifications may be necessary.

910-31358 Instructions (PDF)

Learn more about how adjustable proportioning valves work by reading our tech article. Brake System Selection.  


  1. The brake block is plumbed as follows. The port on the proportioning valve end is the "out" line for the rear brakes. The port between th proportioning valve and brake light switch is the "in" line for the rear brakes. The port in front of the brake light switch is the "in" line for the front brakes. The port on the brake light switch end is the "out" line to the passenger front brake while the port on the bottom is the "out" line to the driver front brake.
  2. This block has individual lines for the front wheels and each line would require a residual valve if the master cylinder is mounted under the floor on the frame rail. 2 psi for each front if it has disc brakes and 10 psi for drum brakes. It still will require a residual valve to the rear with the same psi, depending on the brake type used.
  3. Brake System Builder's Tip (Link)
Some parts are not legal for use in California or other states with similar laws/regulations

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