Advance Timing

Once you remove your flywheel and tap the timing key out of the crankshaft, you can measure the thickness of the key.  You should get a similar measurement to what we're getting here.  Our key is .160" thick.  Our goal is to advance our timing 8 degrees.  We know every .006" we file off the key is equal to 1 degree.  Therefore if we file off .048" we will have an 8 degree timing key.
We put the key in a vice with the flat side of the key up and the rounded portion down.  We have about half of the key protruding up from the vice.  Then we start filing the side of the key.  We will file for a while and take a measurement.  We keep going back and forth knowing every .006" we remove is 1 degree.
We started at a thickness of .160".  We now have a thickness of .112".  We have successfully removed .048" and now have an 8 degree advance timing key.
The filed key now has a step in it like these keys.  We used to sell timing keys already filed however it's easy enough to do this with your stock key in less than half an hour.  
Here is the correct orientation of the advance timing key.  The step you filed into the key is on the left.  Now when you install the flywheel you will gently rotate it clockwise until it contacts the key.  This will leave a little gap on the other side of the flywheels keyway.  We suggest sticking a toothpick in that gap so the flywheel does not roll back counterclockwise when you tighten the flywheel nut.