Starter Problems

[Wootdog]

All,
I have been through three NAPA starters on my truck in the last year. I dont drive the truck all that much. It is a 350/350 combo. The truck only puts out 300 horses. I have checked the teeth on the flywheel and none are messed up. I had a small shim in it. It was paper thin and unreadable as far as thickness is concerned. I didnt put it back on with the newest rebuilt napa starter. What happens is the aluminum case at the front of the starter either cracks or in the last case broke. I pulled the inspection cover off this time and reinstalled the new starter and noticed their isn't a whole lot of clearance but the starter is not touching the flywheel. Previous brands of starters never had this problem. Any help would be appreciated. Kerry