I have a 350 Chevy in an '84 Monte Carlo SS and I keep having problems with the starter. I put the starter and it starts fine but after a few times, i can here it starting to grind a little until it it doesn't want to engage at all. Then I'll crawl under there and shim it with a 1/4 inch washer (wrong, I know) and it will be fine again for a short while and eventually it will do it again. It almost seems to me that it is wiggling itself loose? Any thoughts, ideas, or solutions. I am considering new bolts and I am already using lock washers on the bolts. Also, the flexplate and starter are both new.