Belt problems

Just replaced the engine, and I went to go out the belt back on and it is way to tight it will move on idle… I figured I could put a small spacer in the secondary clutch?? I tried to get the secondary apart but it is weird, it doesn’t have a snap ring like most… It has what looks like a bolt but when I compressed the spring it will not come off?!? But I don’t even know why the belt is tight… It was fine before I did the engine replacement… PLEASE HELP