Mk1 upgraded to Mk11 in Apr / May 1957 from engine no 1425097 bringing it to 51.8hp at 1600 rpm
Shorter push rods (299.7mm)
New injector nozzle N141 (pumps mods not mentioned - may need investigating)
Enlarged bypass port
Different waterpump gaslet
New oilpump with integral PRV, different pickup filter
New pistons
New front engine plate & different sump
New cylinder head with inline ports
Mk111 launched with the Power Major August 1958 engine no 1481091 and
Inc Super Major October 1960 Engine no 1575886
Used SHORTER 'RIGHT HANDED' rocker arms
Reverted to the Mk1 injector nozzles N123
Timing 23 BTDC to accound for modified pump plunger travel
In 1962 FPM (& FSM) from engine no O8B-756398, the Minimec pump with mechanical governor (still marked Simms) was used.
With nozzle, push rod, rocker and pump variations, tread carefully '57 - '62 Major Owners who might have a 'pick & mix engine !

edit to add first PM 7 SM engine Nos from elsewhere