Off the cuff and just curious is there any way there is something tight in the valve train after working on it?
Only reason I ask is I had a GM guy that lived next to me years ago who adjusted the valves bad wrong and all but locked the motor up.
This dumbass ran the stud in the rocker down all the way and backed them off a turn and a half...
Could be as simple as a starter...I did have a cable a couple years back on mine that was corroded in the center about 6" from the battery.
I'd never seen that before...