I have an 85 z28 with a 350 and a t5 i believe it has a 168 tooth flywheel. Well I have a powermaster 9600 starter and i shimmed it and it started fine 3 weeks ago. I don't use the car much so it sat there and i stared it maybe 3 times to drive around and it started fine sat another week i started it and it started right up but 2 days ago i tried to start it and i heard a loud grinding sound so i let off then i tried to start and it stuggled but it started. I drove to teh store waited in the car with it running wife came back and we drove home. I pulled into my garage shut it off and started it and it came on fine. The next day after work i came home to pick up the car and it wouldn't start. it sounded like the starter was spinning but wasn't engaging the flywheel. I kept at it and after several tries it finally engaged and fired up so i drove to my parents house then when i wanted to leave it didn't start again. It just spinned but didn't engage so I left it there. Today i spent all morning on it with no success. I tried different shims on there and it started a few times but is not consistent. Its a bran new starter any thoughts on what could cause this? Could it be taht my batterie is too small:? sounds stupid but maybe its a 450 Cold crank volts or whatever they use to rate it. I also went to local autozone but the idiot behind the counter gave me the wrong starter and it didn't fit in the i think its called bellhousing? It got dark and I was frustraded so i gave up for today but any thoughts on what could cause this?

 

bump any ideas? the car does start from time to time but most of the time the starter just spins but doesn't engage flywheel. When it does engage the flywheel it starts right up with no problems. No grinding noises or anything like that.