I have a 89 Formula with a mildly built 350. In February of this year, I bent a push rod and put my car down for a while. About a month ago I got t up and running again, but when I first tried to crank it over, I heard this horrible grinding sound from the starter. I went to look underneath and the cone cracked. I did that to 3 more oe style starters. I purchased and mini starter and shimmed it appropriately, it work for a little bit but then it look led like the teeth would get stuck in the flex plate until eventually it would spin with out engaging. After that I purchased a high torque starter and that worked for a while as well. Until recently it started grinding again... I have no clue why it keeps doing this. Any ideas on why and how to fix this problem? It has become extremely frustrating

 

Your three most likely possibilities are ;

#1 Despite your best efforts your still not getting them shimmed quite right ,

Or

#2 Your not using the correct starter bolts ,

Or

#3 The holes in your block are drilled wrong and this has the starter an an improper angle that no amount of proper shimming can cure .

If you do a search of this board you will find that #3 is not as outrageous a possibility as it sounds , several threads have in fact dealt with this exact problem , starter holes fractionally off from where they need to be , and for your sake all you can do is hope like Hell your problem lies somewhere with answers #1 and #2 above .

 

If this is a 70s 350 block such as a 010 casting, it's drilled wrong, and you need another block.

Search the site for my userID and the phrase "The Starter Problem" including the "The". I've described it, and some of the other 70s factory sloppy block machine work Problems, in detail, many times over the years.