57 truck brake issue

[lowrodderchev]

Ok here’s the skinny I have a 1979 Camaro clip on my 57 chevy truck under floor master cylinder kit drums in the back. So after driving my truck all day around town I notice the front brakes getting real tight. Not all the time just here and there. Tight enough were you can smell the brakes smoking sometimes so tight it wont move in gear. I adjusted the push rod to where it feels comfortable and not getting tight. So yesterday jump on the freeway after about 35 minutes I use my brakes to find them really low. Scary low. But after pumping them a few times the pressure builds back up I’m good to go. Only happens after driving on the freeway a bit or it sits. I’m running residual valves my front brakes are 14 inches off the ground middle of master cylinder is 11. Any suggestions? Thank you in advance guys