So I have been battling this starter grinding issue for a few weeks now. Here is what I have done. Tried a new starter Shims Checked mounts ensure tight bolts replaced ignition switch The clearance of the pinion and flywheel is exactly 1mm as recommended from the manufacturer. No luck still got grinding. When I start the car for the first time in lets say a week no problems. Then I bring it outside to work on it and fire it up...... back to grinding. Finally today I got a clue. I saw a ploom of white smoke come out of the carb suggesting I may have a backfire which may be rotating the engine in the wrong direction which would play havoc on the starter pinion obviously. Scouring the net I quickly see it is a possibility. When the engine is running it runs fine without misses, backfire, etc. My question is has this happened to any of you or do you have any suggestions, tricks, advise, prayers etc I can use. Sorry I am running I 406 SBC with medium cam and edelbrock 600cfm