It’s always good to learn something and today I learned what year my two Lucas 25D distributors were made. It’s not very exciting but at the same time it can help with identification of engine build years, as long as the distributor is original.

Below is the Lucas distributor from my original 18GB engine. This distributor was made the 12th week of 1966 so it sat around for about 9 months before being mated to my engine that was built in January 1967.

March 1966 Lucas D25 Distributor
March 1966 Lucas D25 Distributor

The distributor from my 18V engine is dated the 48th week of 1973, so November 1973. This is interesting because I have assumed that my 18V engine was produced some time in 1972 by looking at the engine number. The 12H 2923 cylinder head that is on the engine was produced until 1974 1/2 so my engine is likely to be an early 1974.

November 1973 Lucas D25 Distributor
November 1973 Lucas D25 Distributor

From what I can tell the bodies of these distributors are the same but the 1973 unit has a 19 degree cam and stiffer springs while the 1966 unit has a 10 degree cam. I’m assuming this has something to do with emission controls but I’ll have to look into this further. Do any of you have an easy explanation?

10 degree cam on Lucas 25D distributor
10 degree cam on Lucas 25D distributor
19 degree cam on Lucas 25D distributor
19 degree cam on Lucas 25D distributor

The other change is to the vacuum advance unit. Once again I’m not sure what changes were made here, perhaps they are the same on the inside with just a different pipe coupling. The 1973 unit is on the bottom in this photo.

Luca 25D distributor vacuum advance unit
Luca 25D distributor vacuum advance unit

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