My husband is trying to figure out what the spark advance is supposed to be when it is in idle. Our blazer takes a long time to get up to speed and having some other issues and the spark advance in idle is running at 21. I guess this is also called timing advance. I am not sure.

What year and what engine?

It is a 98 with a 97 crate motor. 4.3l

The distributor housing is keyed, meaning it can only be installed in one position and is not adjustable. Ignition timing is controlled by the ECM.