22-02-2022, 11:00 AM
Hi
As far as I know, the model number is made up as:
D = Distributor
J = Model
4 = 4 Cylinder
A = Auto advance
The A in distributor model numbers was dropped in later years when auto advance became universal.
Lucas model numbers like DJ4 and DK4A are only the start. From some time (probably in the 1930's) due to the multiple variants within each model Lucas also used a part number of 5 figures plus a variant letter. The variant letter was for minor production changes over time, and doesn't normally affect interchangeability. Only with this part number can you reference the detailed characteristics.
Probably also worth noting that Lucas convention was always to quote "Distributor Degrees" and "Distributor RPM" in their data, so 7 degrees advance range at the distributor is 14 degrees advance range at the crank. Baseplates are often stamped with a number representing the distributor advance range.
Lucas convention for rotation (CW or CCW) was to define it looking at the driven end, NOT as viewed from the rotor arm. This has caused some grief over the years.
As far as I know, the model number is made up as:
D = Distributor
J = Model
4 = 4 Cylinder
A = Auto advance
The A in distributor model numbers was dropped in later years when auto advance became universal.
Lucas model numbers like DJ4 and DK4A are only the start. From some time (probably in the 1930's) due to the multiple variants within each model Lucas also used a part number of 5 figures plus a variant letter. The variant letter was for minor production changes over time, and doesn't normally affect interchangeability. Only with this part number can you reference the detailed characteristics.
Probably also worth noting that Lucas convention was always to quote "Distributor Degrees" and "Distributor RPM" in their data, so 7 degrees advance range at the distributor is 14 degrees advance range at the crank. Baseplates are often stamped with a number representing the distributor advance range.
Lucas convention for rotation (CW or CCW) was to define it looking at the driven end, NOT as viewed from the rotor arm. This has caused some grief over the years.