New VS Old 340 6-pack

I believe the idle solenoid when energized opens up the butterflies to the idle setpoint. When the solenoid is deenergized by turning the key off, the butterflies close completely and helps prevent engine run on.

I have an old six pack and have not ran an idle solenoid for over 15 years and have had no problems with run on so I don't know if it is really necessary.

Rod