Transmission Controlled Vacuum Advance

System allows advance only when in top (fourth) gear. The system allows vacuum advance during warm up period and ensures satisfactory driving performance after starting the engine. When solenoid valve is energized, a needle valve opens and vacuum advance is eliminated. When valve is de-energized, the needle valve closes and vacuum is introduced to the vacuum unit of the distributor to advance the timing. A gear switch, located on the transmission cover, allows current to flow to the solenoid in all gears except top (fourth) gear.