Gas Question

[Klaus]

There is a good reason to run leaded fuel in older (pre 1975) high performance engines. These older engines did not have hardened valve seats. The lead in leaded fuel lubricated the valves and "cushioned" the valves when they closed on the valve seat in the head. By 1975, unleaded fuel was mandated due to catalytic converters, and hardened valve seats were installed in the heads of all new engines.

Remember that performance engines usually have heavier valve spring pressures to allow the valvetrain to function at a higher RPM before valvetrain "float" occurs.