illf8ed,
I found at least three books I have on the Norton marque that mention the Combat engine being available before '72.
These books are:
'Norton Twins' by Roy Bacon.
In his book Roy Bacon states that the "optional high performance version.....known as the Combat motor..." was available from the middle of 1970 production.
'Norton Motor Cycles from 1950 to 1986' by Steve Wilson.
Also mentions the same.
'Norton Commando' by Mick Duckworth.
In Mick Duckworth's description of the increased performance of the 1972 model he states that: "This was achieved by installing the Combat engine, previously listed as a special order item."
There may be more info available? I will see what else I can find.
It's probable there weren't that many of these Combat engines actually supplied, not for normal road use at least?
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Update
And another reference to this found in:
'NORTON The Complete Story' by Derek Magrath.
