Shimming a starter

[kevncar]

Trying to help a friend get the starter on a blazer he just bought working right. The previous owner had problems with the starter engaging and said he had even spent over 500 dollars at a shop getting a new flexplate and starter put on it. 2 months later it didn't work again.My friend just finished putting a new starter in it and brought it over and it will start but it makes a nasty grinding noise as it does. Thought I'd ask the wealth on knowledge here to help us get the thing shimmed right, or whatever it's gonna take. Thanks in advance.