Turning over problem

[leejoagogo]

I have an 1983 Z38 that i put a GM crate 350 into, recently the ol' 700-r4 started acting up and one day while trying to start the car it sudden'y stopped turning and the force broke the starter housing. i replaced the starter and it won't crank the motor. I have the tranny removered because I am converting it to a 5 speed until i can afford a 6 speed . I was wondering why my motor won't turn. It wasn't low on oil or anything. It was running fine just the day before. I've had it do this before but not to the same extent. The engine would crank but it had a "rough" spot that it would slow through. And this only happens on cold/wet days.