Hy RAC1812, most of the time dieseling can be traced to a throttle that is open too much. Combustion cannot take place without oxygen and a properly closed throttle will not allow enough oxygen to support combustion. Hot spots in the combustion chamber may be ignition points, but without oxygen combustion cannot take place. The o.e.m.s installed solenoids on the throttle linkages in the seventies so that the throttles would close completely when the ignition was turned off. The vehicles curb idle was set using the solenoid which dropped back when the ignition was turned off. So I think you will have to adjust your throttle linkage to close more, get the engine idle r.p.m.down where it belongs, hope that helps.
