Dizzy curve

I ran a "Slanty" :lol: for 10 years in my '68. It liked the initial timing set at 21* with the vacuum advance disconnected while setting it and the advance plate welded and filed to limit the total initial & mechanical advance to 32*.

It ran the best with the vacuum advance hooked up to manifold vacuum, so that at idle the timing was in the mid 30's. As soon as the throttle was opened, the vacuum dropped back to the initial and mechanical totals until mid to higher rpm, which eliminated gas knock, gave incredible low end torque and improved the mileage a bit.

I tried tuning it like the factory recommended, which was based mainly on reducing the NOx emissions, while providing acceptable operation, but the drivability and performance suffered.

The method I used above was based on the Four Seconds Flat literature and numerous variations of that tuning theory to find what the motor liked best.