I second the tight rings. I built an engine a few years back and it was one of my first ones. I built it tight to tolerance. I was friends with a machine shop and asked it to be as exact as possible. I mean I plastiguaged everything, miked, measured, matched. I rustoleumed the water jacket, installed everything I had read about. The engine was a work of art!
I wrecked the donor car. My piece of art sat for about two years. I went to run it in a new vehicle I had worked on, and it was stiff!
I had to take it out and turn the crank with a breaker bar on the flywheel side of the engine. I oiled the cylinders and let it sit.
Once I got it a full turn, it went "easily" like it did fresh.
I believe in my case, the rings just got very used to being where they had been, and everything else had just gotten used to being where it had been.
Plugs out, WD 40, waiting, elbow grease, reinstall, and she fired with lots of smoke. I also cranked for a while with the plugs out before I started it.