Hello Bazza,
It could be that the R is the inital of the original engine builder, or someone who has reconditioned it since, I have three lots of initals now ; P, BZ and another R like yours.
As we live on opposite sides of the country I think it is unlikely that the R stamped on the sump gasket face is from a reconditioner and more likely to be from the original builder at Holden's engine plant in Melbourne.
This R may or may not be related to the R on the engine number pad, in time it may become more clear.
If, as I suspect the R on the engine pad is from the engine builder at Holden, this may account for different engine specs having the R and this would have been placed there prior to the engine number and may account for why it is not in the same allignment.
Mike
I think I have finally worked out what the "R" on some engine number pads is all about!
If we consider that the "R" has shown up in forms that could not have been placed there by Holden manufacturing from the period of 1969 to 1974 at least, then this cuts out most theories and leaves one the most likely.
The most likley answer to my own question is that the "R" means replacement engine. My reasons for this statement is that from a 161 I have here it has a sequential number that would be the same as the original 1969 engine and the prefix is 161R this is of a smaller letter size indicting that it was an unstamped replacement block which had the original engine number and a R stamped by a service person to indicate that it was a replacement block and pistion set, ( not short motor ).
Once NP numbers were used the R also continued to be used, I had wondered if the R stood for relieved block, however as some "R" marked engines do not have the relieved block this does not match, this R looks to have been added later and does not form part of the engine number.
To quote litriture from "Ford" ( sorry about the "F" word ) an "R" was to be used for Ford tractors to indicate a replacement engine, I have two here from the 1930's and they do have an "R" at the beginning of the engine number and these are definately replacement engine blocks with an "R" clearly visable.
To cut a long story short Ford had issued instructions to dealers and agents fitting their exchange new core blocks, that the new engine be stamped with the old number preceeded by an "R" to indicate a new replaced engine block.
In practice not all engines had the old number and the "R" prefix added, which caused no end of problems with parts ordering as the old engine number was the only identifying information available for spare parts ordering.
So the answer to me seems to be that the "R" was likely quoted in a Holden service letter long forgotten, in which dealers were instructed to add an "R" to the engine number pad of Nasco "N" series engines, and that sometimes this was done and at other times it was either forgotten, or the engine fitter could not be bothered.The case for replacement block and piston sets varied from Short motors, in that the "R" was able to be incorperated into the engine number as the whole number was being restamped.( some may recall an engine that came up on Ebay a couple of years back that had no engine number, this was likely a replacement block and piston set in which no one bothered to stamp when put into service )
Of course there is always an exception to the rule, and this was that each state had their own Police numbers for a variety of reasons from the old number being obliterated, a recovered stolen engine, to a mechanic fitting a block and piston set and not bothering to transfer the old engine number to the new block.I hope this goes some way to solving this riddle?Mike73
