One more comment- - - -
Are the front brakes drum, or disc? The check valves are ONLY used for drum brakes, to keep the wheel cylinder cups from sucking air by retaining a little positive pressure in the lines. The shoe return springs retract the shoes from contact with the drums. If a M/C with a check valve in the front brake port is used on a disc brake system, it causes the disc pads to drag and wear, because the caliper pistons don't have return springs. Be sure you get the correct M/C for your application! On a disc/drum system, the combination valve requires about 100 pounds of pressure buildup in the front brake lines to prevent front wheel lockup and loss of steering control in slippery conditions. Sometimes it's necessary to manually release the spring-loaded stem of the combo valve to get pressure to the front brakes during bleeding.
Jerry
