Push rod is straight
I doubt it; When push rods retract as the cam rotates, the valves stick open for a little bit before closing. Engine builder checked this.
Engine sat for about 6 months. Started and broken in by shop that did the installation. They have a lot of experience with hot rods (that's all they do) and they did ask me if it had a flat or roller cam so I guess they know how to break in an engine.
I'm assuming preload was set by by the engine builder.
Engine builder said heads need to come off to see why valves are sticking. How likely is it that bad gas could cause this? Engine builder says very likely. Others have said "maybe but doubtful" to "no way." If it WAS caused by bad gas I guess I just learned an expensive lesson, I just want to make sure it really WAS caused by bad gas and the machine shop isn't just CYA'n themself.