Caliper Piston Retracting

[1Bad68Cat]

Hi everyone,

Need some insight/recommendations. My setup: 66 c10 with 2012 CTS-V brakes front and rear, hydroboost from an Astro Van, and Corvette 1-1/8" bore master. I was doing some maintenance/suspension work and noticed that the caliper pistons/pads have retracted from the rotor approximately 1/8" on each side of each rotor. I pump the brakes to reseat, but later in the evening I saw that the pistons/pads had retracted again. This may explain the not so great pedal first thing in the morning when leaving the house for work. This has been going on for some time but didn't think much of it because brakes always felt good after pumping them in the morning. Does anyone know if the cast iron corvette masters come with residual valves? Would it be a good idea to install 2lb residual valves to prevent the pistons from retracting? What other parts should I look at to prevent this? Appreciate any help I could get.