Odd=fire distrigutors were used on the early Buick 231 V6 engines and had an oddball spacing of the plug wires in the distributor cap. Two wirea sre close togethert, then a wide gap, one wire, another wide gap, and two more close-spaced ones. The crankshaft rod journals are also spaced unevenly. The engines shake on the motor mounts at idle due to the uneven firing impulses. Even-fire distributors have sic equally-spaced plug wtre towers. Any Chevy, Pontiac , or Oldsmobile inline six HEI diastributor is an "even-fire" type.
jerry
