Quote Dean: "The original part number for the upper tensioner is 13080-25500. In a SR catalog dated 1968.6 it shows the part number in the drawing and the parts list as 13080-25500. However, In the back of the book the part number listing supersedes from 13080-25500 to 13080-25501. The last number, in the Nissan part numbering system, denotes a distinction, a change in the part "
The only original number I found is 13080-25501, the "255" stands for the model, which is indicated as a SR(NOT L)311-U 1967.5 2000 U20 series engine low wind screen. I would think if it superceeds in the later 1968 U20 and on engines with the high windscreen model you would think the model number would change . If it was for example "259" it stands for a SR(no L)311-U 1968 2000 U20 series engine high windscreen. But it seems they only changed the last 2 numbers (which are distinction numbers), 00 to 19 are "similarity" kinds of distinction numbers, but no idea what is changed to the part or what they mean with similarity change 00 to 19, because there is also a similarity numbers 60 to 69.
The only thing written about it;
It could be something small like a recess (but could also be a color if it was an interior partnumber).
Other distinction number series are for "material", "processing" and "exclusive service use" but 01 does not fall in those series numbers...
Fact is,
"there is made a very minor change to the part that is not significant enough to warrant a complete new part number"
Anyway maybe DEF (davdav2000?) has or can digg up some books to check/shine a light on this "similarity" distinction number meaning. Or on the given part-numbers for the upper tensioner, which not changed for SRL and/or 1968-1970 2000's.
You can find information on line defining part number info. My info came from an ordering rep at Nissan who worked at LAR in the 90's
D-
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Just to add to the confusion, I have six used upper tensioner bodies that I acquired in the 1980's. They were in the spare parts stash of a well known U20 race engine builder. All of them have the rough casting and I'm pretty sure he acquired them from Nissan in Southern California.
if it superceeds in the later 1968 U20 and on engines with the high windscreen model you would think the model number would change
. If it was for example "259" it stands for a SR(no L)311-U 1968 2000 U20 series engine high windscreen. But it seems they only changed the last 2 numbers (which are distinction numbers), 00 to 19 are "similarity" kinds of distinction numbers, but no idea what is changed to the part or what they mean with similarity change 00 to 19, because there is also a similarity numbers 60 to 69.
