Proportioning Valves
Proportioning valves come in various shapes and sizes depending on the car you have and modifications to the braking system. Proportioning valves are used in disc/drum brake systems to provide the correct pressure for front disc and rear drums. Four wheel disc valves are also available. The valves and distribution blocks available are listed below.
The first year for disc brakes on GM and Chrysler products was 1967, Ford was 1966. All American cars built prior to this had four wheel drum brakes. Disc brakes were introduced as an option from 1967-1972. Starting in the 1973 model year, front disc brakes were primarily standard and front drums were rarely available. The dual master cylinder that separates the front and rear braking systems was introduced and standard on all cars in 1967. Therefore, all 1967 and newer cars came with dual master cylinders from the factory. Disc brakes require over three times the line pressure of drums, so the master was divided to provide pressure to the front and rear separately. This also meant that if a front line blew out the car would still have pressure to the rear brakes and vice versa.
GM Distribution Blocks - F/X body, Camaro, Firebird, Nova
GM Distribution Blocks - A-body Chevelle, GTO, 442, GS & Monte Carlo, Grand Prix
GM Full Size and Other Makes
Disc Brake Conversion Valves & Lines
Proportioning Valves Applications
Proportioning Valves / Brackets
Mopar Valves
In 1971 for GM and 1972 for Chrysler, the one piece combination valve replaced the multiple piece design. The combination valve keeps front and rear systems separate, splits the left and right front lines, houses the sending unit for the brake failure warning light and provides the proper brake line pressure for the front disc and rear drum systems. This is why it is important to know what is correct for your car and how your car can (or will) be converted from drum to disc. There are three basic disc conversions for 1967-70 cars: 1) Factory original conversion, 2) Combination valve conversion and 3) Adjustable valve conversion. Each conversion has its benefits. The staff at Inline Tube will help you determine the best disc conversion configuration for your vehicle. Valves, distribution blocks and dual master conversions are illustrated and listed below.
Chevy Truck Valves
All 1967-68 GM factory disc brake cars came with dual piston calipers. If the car is a 1969 or newer car, it came with single piston calipers. All aftermarket conversions come with the single piston calipers, but they are not factory correct for the 1967-68 cars. The single piston conversion will bolt on 1964-72 GM A-Bodies, 1967-69 F-Bodies and 1968-74 X-Bodies and function perfectly.
Since disc brakes were new in 1967, the valve was still being worked out for the next few years. The 1967-70 valves could consist of as many as three elements and the valves would not work properly without all the pieces. Both 1967-70 factory drum and factory disc cars have (or had) a distribution block which is identical whether the car was drum or disc. Although very similar in appearance to a proportioning valve, the distribution block does not alter brake line pressure. The distribution block keeps front and rear systems separate, splits the left and right front lines and houses the sending unit for the brake failure warning light. The 1967-1970 factory disc vehicles employed an additional valve, referred to as a hold-off valve, mounted at the master cylinder. The final component in the 1967-70 factory disc brake systems was a correction valve typically located in the front to rear brake line for the rear brakes. This valve was not used in every factory disc brake car, but would make the front to rear line two pieces with the valve usually found mounted near the floor pan of the car. An original 1967-70 disc car can be factory correct without the correction valve, but not without the hold-off valve at the master cylinder.
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