[Bob Bidonde]

Both of my Model "A" cars have high-compression cylinder heads. I fully retard the lever to start them, pull it halfway down to warm them up in the winter and go to full advance for all driving except on hills. When approaching a significant hill, I retard the spark 2 to 3 notches.

With today's 87 Octane gasoline, the Model "A" and Model "B" engines can run with more advance than the 20-degree limit. All of the stuff in vintage publications re spark advance was for 40 to 60 Octane gasoline without any anti-knock additives.