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Inline Tube - Proportional Valve Installation Instructions

Proportioning valves provide four functions:

  1. Proportion correct pressure to the front and rear braking systems. 
  2. Provide 10psi residual pressure in the brake lines. 
  3. Is a metering valve to apply pressure to the rear brakes before the front brakes. 
  4. Has a brake warning light to detect a loss in pressure.

In some cases, the right front line will be plugged at the proportioning valve and the left front line will go to a "T" fitting. From the "T" fitting, the front lines then split off and go to the left and right front wheels. 

Our proportioning valve has a dashboard warning light switch built-in (this is not a stop light switch). The warning light will indicate any loss of pressure, for example, a leaky wheel cylinder. We recommend you wire this light into your system. Any two-wire light socket will work. One wire goes to the accessory power and the other goes to the warning light.

Adjustable proportioning valves have a knob that allows you to set the intensity of the rear braking action. This valve can be added into the rear line(s) anywhere you choose. Once fitted with lines bled completely, the optimal setting can be determined one quarter turn at a time. 

When replacing a proportioning valve with a duplicate, compare the two valves for similar mounting holes, port configuration, and warning light connection. Then mount and fit the lines as was previously done. When replacing an existing proportioning valve with a different design, you need to consider the other elements in the braking system such as separate blocks and/or correction valves. Typically the new proportioning valve replaces all of these elements, which is why these contemporary valves are also called combination valves. This means that these other elements in the system that were part of the original set-up are now replaced by the one new proportioning valve. This situation is specifically for original disc brake cars from 1967 to 1970. In 1971 and newer, the combination proportioning valve was used from the factory. Replacing a multiple valve and block system results in different brake lines and routing.

If you are converting to front disc from an original drum car, you will be adding a proportioning valve to the system for the first time. The key to success for a disc conversion is to plan ahead and walk through your entire installation prior to turning wrenches. Where you mount the valve you can greatly impact the brake lines and will be available for the conversion. The adjustable valve is covered above; the pre-set combination valve is now our concern. To facilitate most brake line conversion kits and provide clearance for headers and large valve covers, the proportioning valve will be mounted at the master cylinder. Inline Tube provides proportioning valve mounting brackets that use one of the master cylinder mounting bolts to place the valve next to or under the master cylinder. Our conversion line kits are designed for this popular application. The further you choose to “customize” your installation, the less available bolt-on parts will be. This means that you will have to alter provided components or fabricate your own solutions. In general, Inline Tube provides lines for either factory original or prop at master conversions.

Consult your mechanic

This page is intended for use as a basic guide to help install new brake and fuel lines. If you are unsure about any part of the installation procedure, please consult a certified professional mechanic for assistance. Inline Tube assumes no responsibility or liability for improperly installed lines. 

Quick Tip: Installation

Valve Installation - Refer to the disassembly photos. There are many holes in the frame and it is impossible to remember which are the correct holes for mounting. If you do not have photos, many parts retailers and Inline Tube sell factory assembly manuals that show in detail where each of the parts are located on the car. The manuals are available for cars such as Camaro, Chevelle, Nova and Corvette through Inline Tube.


Inline Tube - Brake & Fuel Lines

15066 Technology Drive
Shelby Twp, MI 48315
(586) 532-1338