What purpose does the ballast resistor mounted to the firewall on my 58 Ford serve? I am having a problem of an intermittent drop in revs to zero. The car
starts up quickly and runs fine, except for this. It happens under various situations, I cannot isolate it to any one specific situation. It's a 292, points distributor, 2bbl Holley, all in good working order.
Also, where is the search feature on this site? This may have been answered on another post, but I am not smart enough to find the search box!

The Ballast resistor drops Voltage from 12 down to about 9 once the Car is running. Bypassed for 12 Volts to start the Car. If the Ballast resistor burns out the car won't stay running when it starts. The Resistor is either good or burned out. Will not be the cause of your random problem. Have a look at the little braided wire that connects the Points to ground inside the Distributor. They sometimes break and no ground occurs intermintently. Also possible Condensor problem. Try another Condensor preferrably  American made not offshore Junk.

  

The ballast resistor is there to save your points from burning up. That's it. If you change to an electronic unit like the Pertronics, you can chose to leave it in the circuit or take it out. Good luck.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Thank you both for the replies! I will dig into the distributor.  It is not easy to get at the points on this car!

Oldcarmark is on the money. The coil is designed to run on 9v. When cranking, the large draw from the starter motor causes the voltage to drop. If the coil was designed to run on 12v, when cranking the voltage would be too low, creating a weak spark when starting. When starting, the resistor is bypassed to compensate for the voltage drop.

Thanks,I found the issue.  The wire from the distributor to the coil was about to break.

Well I was pretty close. Good that You found the Issue. Its always best to check the simple stuff first before looking for a major cause of a problem.

  

Those are excellent words of wisdom, but, sadly I usually think worst case scenario first!

Most People do including Me but its usually the simple things that cause most Problems. You don't need an Engine Overhaul just because one Day it won't start.