Engine Timing 101:
Regular production distributors have timing advance that starts at 700-900 RPM. The timing advance in distributors used in high performance engines starts at 1100-1200 RPM.
1.) Engines equipped with some high performance camshafts will not idle below 700 RPM.
2.) Since the centrifugal advance in a stock distributor starts at 700 RPM, you cannot set the initial timing.
3.) In order to lock down the initial timing in a engine e/w a high performance camshaft, you must have a distributor that starts the centrifugal (mechanical) advance at 1100-1200 RPM.
A distributor with a higher RPM centrifugal advance mechanism will allow you to turn the engine idle speed low enough so you can set the initial timing before the centrifugal advance starts. After the initial timing is locked by the distributor bolt, you can then turn the idle speed above 1100 RPM and observe the initial timing plus the centrifugal advance.
If your timing is 22 degrees BTDC, the initial timing is 12 degrees BTDC with 10 degrees timing advance in by 1200 RPM. .