anyone had ever issues with prop.valve

On drum brake cars there is a residue valve in the master cylinder that keeps a couple of psi of pressure in lines and wheel cylinders to prevent air from be sucked in past the seals. I had a similar issue once where these valves were getting plug up with gunk and after several applications of the brakes they would drag and it would take awaile for them to blled back down.

Also, as Vdart stated the drum brake cars do not have a proportioning valve, it's just a distibution block with a switch between the front an back to trip the warning light if one side fails.