early post-war single engine evolution

I have acquired a project ES2 that has both 1947 and 1948 engine parts. I believe the 1947 engine uses lever followers as a continuation of pre-war practice and the 1948 uses axially sliding tappets acting on the cams to transfer motion to the pushrods. I seems to me that there was significant evolution of the engine post war and I am unclear as to which parts will fit which years. For example, are the head and barrel the same for 1947/1948? I know the rocker box is different between these years but cannot find amy discussion of the year to year evolution of the pushrod 79x100 engines. If anyone would like to explain the evolution of point me to where this is discussed, I would appreciate it. Thanks in advance.

ilikevelos said:

I have acquired a project ES2 that has both 1947 and 1948 engine parts. I believe the 1947 engine uses lever followers as a continuation of pre-war practice and the 1948 uses axially sliding tappets acting on the cams to transfer motion to the pushrods. I seems to me that there was significant evolution of the engine post war and I am unclear as to which parts will fit which years. For example, are the head and barrel the same for 1947/1948? I know the rocker box is different between these years but cannot find amy discussion of the year to year evolution of the pushrod 79x100 engines. If anyone would like to explain the evolution of point me to where this is discussed, I would appreciate it. Thanks in advance.

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Roy Bacon’s “ Norton Singles “ details year to year changes of the single cylinder models . I have a copy somewhere and I can look up specific questions if I can find it .

The copy on the right is more comprehensive- covers 1927 through 1966 . Appendix covering changes is 23 pages .

ilikevelos said:

I have acquired a project ES2 that has both 1947 and 1948 engine parts. I believe the 1947 engine uses lever followers as a continuation of pre-war practice and the 1948 uses axially sliding tappets acting on the cams to transfer motion to the pushrods. I seems to me that there was significant evolution of the engine post war and I am unclear as to which parts will fit which years. For example, are the head and barrel the same for 1947/1948? I know the rocker box is different between these years but cannot find amy discussion of the year to year evolution of the pushrod 79x100 engines. If anyone would like to explain the evolution of point me to where this is discussed, I would appreciate it. Thanks in advance.

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PM sent .

First of all thank you for your response and information. I actually have the later Bacon book and so I knew the differences at the level. What is more difficult is to determine what parts fit what. My project bike came with both a 47 and 48 bottom end. It also came with two barrels and heads. Both of the barrels and heads appear to be the same. The barrels both have fins that appear to be for an earlier? engine with parallel pushrod tubes while both the 47 design and 48 design have pushrod tubes that are closer together at the head than at the bottom end. I am wondering if the heads and barrels of these two designs (1947 and 1948) are the same even though the bottom end including cams and followers and flywheel and rocker box are different. It appears to me that the 47/48 redesign did not change the barrel and head but hope that someone here will know.

All of the parts I have are disassembled and I will try to look for the rocker boxes and pushrod tubes and report tonight. Ideally, I would have a parts list from the 47 engine, a parts list form the 48 engine and be able to compare part numbers. I would also be great to have the part numbers for a late prewar engine to see the similarity between that engine and the 47. I would like to get another single on the road and it is a little more difficult than I expected give the year to year changes implemented by Norton.

This is the exact form of motorbike archeology I enjoy. Thanks in advance for any further comments.

I should think that the convergent pushrod tubes would have different barrels, head and rocker box as the finning was relieved to accept them - should be easy enough to tell from photos.
Also , if you haven’t already done so it may be well worth your while to join the UK based Norton Owners Club . Great font of knowledge for the non-Commando models . Mike Pemberton is the ES2 motor guru .
I have the Main -Smith reprints of the Workshop Manual and Parts list for 1950 if that is any help . I don’t know if these are still available but if so you should be able to find them for the years in question. Very economical and worth every penny.

Richard Tool said:

I should think that the convergent pushrod tubes would have different barrels, head and rocker box as the finning was relieved to accept them - should be easy enough to tell from photos.
Also , if you haven’t already done so it may be well worth your while to join the UK based Norton Owners Club . Great font of knowledge for the non-Commando models . Mike Pemberton is the ES2 motor guru .
I have the Main -Smith reprints of the Workshop Manual and Parts list for 1950 if that is any help . I don’t know if these are still availability but if so you should be able to find them for the years in question. Very economical and wort every penny.

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Thanks for the info. I will definitely join the uk voc before I start the restoration. Also, racing norton has pretty good engine spares and I am sure will help at the appropriate time.

I am still trying to investigate part differences but have learned that the Model 18/ES2 engines can loosely be grouped into 1926-1929(valve adjuster on front or pushrod end of rocker), 1929-1937(valve adjuster on valve end of rocker), 1938-1947(valve adjuster on top of pushrod, lever follower), 1948-1955 (valve adjuster on pushrod, mushroom follower), and 1956 to end. At least he flywheels, cases including cam geometry, and rocker box changed between 47 and 48. There are many year to year changes but a main change to the head appears to be from 1937 to 1938 with enclosing the valves. I actually think the 1938 to 1955 heads may be the same with different rocker boxes but do not yet have any definitive information on this point. Agree that barrels were likely different. I will investigate what manuals I have and then report. The edgar franks manual is apparently one of the better explanations but is maybe difficult to find now.

I have to say I love figuring this stuff out. After completing my current restorations (a c touring rapide and b rapide) this is the next bike in the queue. I will get to studying the rocker boxes I have soon.

ilikevelos said:

Thanks for the info. I will definitely join the uk voc before I start the restoration. Also, racing norton has pretty good engine spares and I am sure will help at the appropriate time.

I am still trying to investigate part differences but have learned that the Model 18/ES2 engines can loosely be grouped into 1926-1929(valve adjuster on front or pushrod end of rocker), 1929-1937(valve adjuster on valve end of rocker), 1938-1947(valve adjuster on top of pushrod, lever follower), 1948-1955 (valve adjuster on pushrod, mushroom follower), and 1956 to end. At least he flywheels, cases including cam geometry, and rocker box changed between 47 and 48. There are many year to year changes but a main change to the head appears to be from 1937 to 1938 with enclosing the valves. I actually think the 1938 to 1955 heads may be the same with different rocker boxes but do not yet have any definitive information on this point. Agree that barrels were likely different. I will investigate what manuals I have and then report. The edgar franks manual is apparently one of the better explanations but is maybe difficult to find now.

I have to say I love figuring this stuff out. After completing my current restorations (a c touring rapide and b rapide) this is the next bike in the queue. I will get to studying the rocker boxes I have soon.

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Is the cam geometry change you mentioned the eased ramps ( quieting)
for noise reduction? If so I believe the stamping on the cases should have a “ Q” prefix.
Also ( You have done your homework I know ) in the unlikely event that this got by you the cams in use with the footed followers have their inner faces relieved to clear the foot .

I am not surprised by q cams as I have encountered this change in other marques. I believe the footed followers have a lot of variation, with some being intended to rotate and others locked against rotation. Now I need to find some parts books to see the barrel and head part no changes. Both barrels I have look like 48 later ones but until I put the bottom end, barrel, head, rocker box and pushrod tubes together I will not really know. Also, I know the flywheels are different so are the 47 and 48 barrels the same height? I think so but another data point.

I want to build the 47 engine which is correct to the frame but I may have more 48 parts. The 48 engine is an original model 18 engine.

Fun with old motorbikes. M

ilikevelos said:

I am not surprised by q cams as I have encountered this change in other marques. I believe the footed followers have a lot of variation, with some being intended to rotate and others locked against rotation. Now I need to find some parts books to see the barrel and head part no changes. Both barrels I have look like 48 later ones but until I put the bottom end, barrel, head, rocker box and pushrod tubes together I will not really know. Also, I know the flywheels are different so are the 47 and 48 barrels the same height? I think so but another data point.

I want to build the 47 engine which is correct to the frame but I may have more 48 parts. The 48 engine is an original model 18 engine.

Fun with old motorbikes. M

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I think the barrels should be the same height as the stroke was kept the same ( and the rod length? ) while the flywheel change was the diameter was made smaller ( so the piston skirt could be made longer ) but the width of the wheels was increased
( I assume to keep the mass the same ) .

If you join the UK NOC they have a very good online library with parts books etc.

Found some errors in old parts books. Sales brochures made before machines was built with incorrect pictures and specifications. Tales from people who don't really remember details correct. Sometimes lies. Machines fitted with wrong parts. Later modifications. Critical thinking needed when working with historic machines.

Mike40M said:

Found some errors in old parts books. Sales brochures made before machines was built with incorrect pictures and specifications. Tales from people who don't really remember details correct. Sometimes lies. Machines fitted with wrong parts. Later modifications. Critical thinking needed when working with historic machines.

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Absolutely, and even then it is very easy to use the wrong parts.