drum brake proportioning valve

Silent Thunder said

New master cylinder is because I went from single to dual. Brakes function fine other than hard pedal with a excessive travel. I think I need the valves to place the 10 pounds of back pressure on the system.

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If it a master cylinder for a 4 wheel drum brake car it already has the valves in both sides. The 1st thing I would do as long as its the correct master cylinder check to be sure your wheel cylinders dont have frozen pistons. If it is for a disc drum combo it wont work correct in your system.