340 K Member ??

Could it be because of the engine colors? Seems like the earlier years there was no washer, and the 318 and 340's were different colors.

The later years, 318's and 340's were both blue and thereby possibly confused for one another as they came down the assembly like already mounted the the K member.

Maybe the washer was used to differentiate 318's from 340's in that respect?

Could it be, or is this a far fetched explanation?