A Revolting Development
Q. I've decided to backdate my street rod and replace the alternator with a generator. I have the generator and the regulator mounted and wired but I'm confused about the process of polarizing. Why's it necessary, what's it do, and how does it do it?
Vince Carol
Via the Internet
A. Let's start with the basics of how a generator works. When a loop of wire passes through a magnetic field, electrons in that wire will begin to flow-in a generator there is an armature that is essentially lots of wire loops that rotates between two magnets called field windings. The voltage and current delivered is a function of the magnetic field's strength and how fast the armature is spinning in that magnetic field.
This diagram shows the basic...
This diagram shows the basic configuration of a generator. The armature is made up of loops of wire-as it spins a magnetic field current moves through the loops of wire and is delivered through the commutator contacts (which are the ends of those loops of wire) through the stationary brushes (that make contact with the spinning commutator) and current is delivered to the load.Generators can work with either a positive or negative ground system (and since you're replacing an alternator, your car is probably the latter) but they have to be polarized appropriately-that means establishing which field winding is the north pole and which is south, and that determines which way the current flows in the generator.
Henry Olsen of Ole's Carburetor...
Henry Olsen of Ole's Carburetor and Electric (olescarb@sanbrunocable.com) supplied this polarizing guide. Note the difference in procedure between the Ford and the GM/Mopar systems.
Another Revolting Development
Some time ago we dealt with the subject of miss-firing engines, an issue we were experiencing along with several of our readers. Although the severity of the problem varied, the source of it in all cases was traced to cross firing ignitions, which was the result of moisture and crud accumulating in the distributor caps. Now it would seem that if there was a problem with moisture in the distributor cap the cure would be to seal it more effectively, but what we found out is that it's more effective to give it a way out and, thanks to Todd Ryden of MSD, we now know why.
When discussing the issue with Todd the first thing he asked was if all those having this issue lived in high-humidity areas and the answer was yes. According to Todd, high humidity means the ignition system is much more susceptible to carbon tracking or spark scatter due to condensation buildup but another problem is called ionization.
Ionization occurs when the air inside the cap becomes electrically charged and the result is spark scatter or crossfire. Ionization is more prevalent in smaller distributor caps and in areas of high humidity, and even though MSD rotors are equipped with high vanes to stir up the air, ionization can still take place. But for every problem there is a solution, and a simple means of prevention in this case is to drill a pair vent holes in the cap to release pressure and introduce fresh air. These holes should be at the height of the rotor skirt, a 1/4 inch in diameter, and positioned roughly across from each other and away from the intake manifold. In dusty conditions screens should be epoxied over the holes-MSD offers a pre-drilled cap for GM window style caps, PN8438. Of course the easiest cure if clearance isn't an issue is the use of a large diameter cap, such as the MSD Cap-A-Dapt, PN 8420 and PN 8445 or the Pro-Cap, PN 7445.
It looked like moss was growing...
It looked like moss was growing inside our distributor cap and, under a heavy load, this conductive crud caused the spark to jump to the wrong terminal resulting in a nasty miss.
Drilling a pair of holes in...
Drilling a pair of holes in the cap (only one is visible here; see arrow) cured the problem. As this is a front mount Flathead distributor the holes were located 45 degrees from the bottom on each side.