Dwell is the amout of degrees of distributor rotation that the points are closed. Dwell is usually close to 50% of the allotted time for each cylinder. The larger the dwell (kettering) the longer the coil is turned on and the greater the saturation of the buildup of magnetism in the coil body. As RPM increases, the time allotted, in milliseconds, decreases. If 8 cylinders in a car turning 4500 rpm are discussed we can see that the saturation time per spark goes way down. But !!! the % of on time remains the same at about 50%. Thus the coil heat buildup is the same at all speeds except stopped. When stopped, the coil is almost always on if the key is on. Thus burning up the coil because its duty cycle is 50%, not 100%. Mags need rotor speed to make sufficient voltage when hand cranked (essentially no rpm) and thus must have an impulse coupling to hold back, then release the rotor so it spins as fast as the tractor Idle speed or more. at that RPM the energy is saturating the primary windings and coil very well. Thus the magnetism is sufficient to build magnetism in the coil laminations and throughout the secondary windings such that when the points break, the collapse is sufficient to build voltage till the resistance of the gaps is overcome. Remember that at higher RPm the time for saturation buildup is reduced for both Kettering and mag systems. I hope this helps. Jim
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Today's Featured Article - Earthmaster Project Progress Just a little update on my Earthmaster......it's back from the dead! I pulled the head, and soaked the stuck valves with mystery oil overnight, re-installed the head, and bingo, the compression returned. But alas, my carb foiled me again, it would fire a second then flood out. After numerous dead ends for a replacement carb, I went to work fixing mine.I soldered new floats on the float arm, they came from an old motorcycle carb, replaced the packing on the throttle shaft with o-rings, cut new ga
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