[1928Pickuppain]

Heres one id take a look at that would explain it you have gotten the motor up to operating temp a few times now and the metal will have expanded and contracted a few times. Metal never truly goes back to it's origional size once it's been expanded a few times maybe when you did your valves the first time they were just seating now that Thebes expanded contracted there no longer seated at all and may be letting the air pass by them ( this happens to me recently on a 83 iron head I built for my brother) try resetting the valves. Also before you do that rotate your engein while you watch the valve train rise and fall untill you get cylinder no.1 to it's compression strok (both valves "should" be seated at this point) then put it in gear with the ebrake on and hook your compression tester end up to your compressor presurize the cylender with 100 psi down into the plug and listen to were it's coming out wether it's coming from the valves, around the head gasket, or blowing past te rings and out of the vent tubes this is a good way to diagnose were to start.