I apologize for a total timing 101 question. I have "been out of cars" for 20 years (since my teens) and have never REALLY done timing right anyway. Here is my question. I have an HEI in my 68 and understand the idle timing adjustment(rotate the dist to taste), and I somewhat understand vacuum advance timing (which I don't know if it's adjustable on my '75 dist), but, I don't understand how to adjust total timing. Is it with the weights or springs inside the distributor? Also, do you check total timing with vac line disconnected and plugged? Thanks, Jason