Sounds like you need to shim the starter. Shims come in a 2 pack or 4 pack and you have to put them between the starter and block, through the bolt holes. Start with 1 shim and try it for a day. If the starter still does not engage flexplate fully, try another shim.
Could also be the solenoid not fully engaging or releasing.
Shims $5-6 Solenoid $10-15. Never hurts to have a spare solenoid on hand.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
