how do you properly shim the starter on the lt1 and what exactly does it mean to shim it ?

 

It's just a thin piece of metal that goes between the starter and the engine, all you do is loosen and take out the outer bolt (the one to the passenger side), and loosen (but don't completely remove) the other one. Then you slide the shim in. One end is forked so that it will go around the bolt you left in, then just put the other bolt back in and tighten them both down. Easy!

 

The proper way is to actually measure the gap between the starter gear and the flywheel(flexplate) gear using a "wire" gage. However you can tell by feel if you've done enough of them.

 

^^^ is correct, but I've never done it with the transmission attached so I don't know how to do that in car. If the motor is on a stand it's easy.