I do kinda wonder about GMs reasons for making the change to the coil in cap setup. Maybe it was just cheaper to build or assemble. Or maybe there were issues with the earlier short cap/ rotor design? Would be curious if anyone knows anything about that.
Auto mechanics instructors back in the 1960s-1980s got to attend "new products" training sessions at GM training centers during the summer break. The closest one to my school was Memphis Tennessee. The reason we were given for switching to the "coil in cap" setup was to minimize the tendency for high voltage to "flash over" from the cap to the distributor housing in case a plug wire came loose or got open circuited. They over-engineered those early HEI systems because of the 50 KV+ capacity of the coils. They also had to make a thicker rotor center after a couple of years of production- - - -the spark from the coil in cap system would drill a hole in the early rotors and fire straight to the centrifugal advance in case of an open circuited plug wire.
Jerry
