Distributor recurve

For vaccum advance testing .One simple in the drive way test. fully warmed up. Normal lean cruise carb, engine under load from alternator. Rpm around 2000 -2200 with vaccum gauge hooked up advance and retard timing to find the exact point where max vaccum occurs. Check timing ,put that number in your note book.Next with hand held digital tach note rpm.Engine should be runing smooth at this point. Slowly advance timing rpm may rise slighty, advance timing till rpm starts to drop, check timing make note.Some where between these two points is where vaccum advance should be. If more timing is added rpm will drop and engine will start runing rough. Air/fuel ratio will have some effect