When you assemble the timing side cover, it is critical to use the proper thickness timing cover gasket. This sets all the end play clearances for the cams and idlers, and also affects the depth of the engagement of the worm nut into the oil-pump drive spindle teeth.
You can't just go throwing any old gasket in there. There are several thicknesses of gaskets for the timing side, and if you don't know which one was on there when you took it apart, then you need to re-set all your end-play clearances with the proper shims and your spindle drive engagement.
This is why I always recommend that people try to preserve their timing cover gasket when they take it off. And always check to see that the engine freely rotates by hand after tightening up the timing cover. If you have it too tight, the engine won't turn, and severe binding will occur on the shaft. Also, if you changed oil pumps, you need to be sure that they also turn thru the entire rotation smoothly because they are known to sometimes not fit well and they can lock up the whole works.