The unequal spacing of the compensated cam lobes, although  it provides the same relative piston position for ignition to  occur, causes a slight variation of the E-gap position of  the rotating magnet and thus a slight variation in the high- voltage impulses generated by the magneto. Since the spacing  between each lobe is tailored to a particular cylinder of a  particular engine, compensated cams are marked to show  the series of the engine, the location of the master rods, the  lobe used for magneto timing, the direction of cam rotation,  and the E-gap specification in degrees past neutral of magnet  rotation. In addition to these markings, a step is cut across  the face of the cam, that, when aligned with scribed marks  on the magneto housing, places the rotating magnet in the  E-gap position for the timing cylinder. Since the breaker  points should begin to open when the rotating magnet moves  into the E-gap position, alignment of the step on the cam with  marks in the housing provides a quick and easy method of  establishing the exact E-gap position to check and adjust the  breaker points. Another part of the breaker assembly is the cam follower,  which is spring-loaded against the cam by the metal leaf  spring. The cam follower is a Micarta block or similar material  that rides the cam and moves upward to force the movable  breaker contact away from the stationary breaker contact  each time a lobe of the cam passes beneath the follower. A  felt oiler pad is located on the underside of the metal spring  leaf to lubricate and prevent corrosion of the cam. The secondary circuit contains the secondary windings of the  coil, distributor rotor, distributor cap, ignition lead, and spark  plug. The secondary coil is made up of a winding containing  approximately 13,000 turns of fine, insulated wire; one end  of which is electrically grounded to the primary coil or to  the coil core and the other end connected to the distributor  rotor. The primary and secondary coils are encased in a non- conducting material. The whole assembly is then fastened to  the pole shoes with screws and clamps. The breaker-actuating cam may be directly driven by the  magneto rotor shaft or through a gear train from the rotor  shaft. Most large radial engines use a compensated cam that  is designed to operate with a specific engine and has one lobe  for each cylinder to be fired by the magneto. The cam lobes  are machine ground at unequal intervals to compensate for  the elliptical path of the articulated connecting rods. This  path causes the pistons top dead center position to vary  from cylinder to cylinder with regard to crankshaft rotation.  A compensated 14-lobe cam, together with a two-, four-,  and eight-lobe uncompensated cam, is shown in  Figure 4-9 . When the primary circuit is closed, the current flow through  the primary coil produces magnetic lines of force that cut  across the secondary windings, inducing an electromotive  force. When the primary circuit current flow is stopped, the  magnetic field surrounding the primary windings collapses,  causing the secondary windings to be cut by the lines of  force. The strength of the voltage induced in the secondary  windings, when all other factors are constant, is determined  by the number of turns of wire. Since most high-tension  Figure 4-9.  Typical breaker assemblies. 4-6 Two-lobe cam Four-lobe cam Eight-lobe cam Compensated 14-lobe cam Figure 4-8.  Pivotless type breaker assembly and cam. Secondary Electrical Circuit