What I need to know is this a must to have? What does it do? Thanks Steve

This is only necessary if you have an engine with a really big cam that idles very fast and diesels and won't shut off when you turn the key off. What you can do is install a stop solenoid hooked up to ignition power, on when the key is on, off when the key is off. Adjust the idle speed with the plunger on the solenoid, back the idle speed screw in the carb way off. When you turn the key off, the plunger collapses and slams the throttle clear shut, killing the engine. This is sort of an extreme measure for cars with very agressive cams and high idle speeds up around 850 --> 1000 rpm.

Idle stop solenoid can also be used to bump up idle speed to better handle a major accessory load like air conditioning.

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Fred Aldrich
Web Site: www.GeoCities.com/~69_chevelle (http://www.GeoCities.com/~69_chevelle)