I have a 1973 Z/28 with the original Muncie M21 4-speed transmission. I've owned the car for almost 50 years and I'm noticing that I have to push the clutch pedal in more than I used to for the interlock to disengage so the car will start. Can someone explain to me how the interlock system works? What exactly is happening when I push the clutch in? Does that engage a switch under the dash (like the brake pedal closes a switch to light the brake lights) or is there more to the mechanism? Any help is appreciated.

 

It is much like the brake switch. Its is a clutch safety switch but many manufactures still call it a neutral safety switch. On older cars it is very simple. Power comes from the ignition switch through the clutch switch to the starter. With the clutch pushed in the switch allows power through. With the clutch pedal released it it does not allow the current to flow through it.