Noticed your comment about cam lobe wear......not a surprise and a common problem on Norton Dommy and Commandos(or Atlas Mk3 as shown on factory drawings at one time!!). I am copying part of an epistle i wrote MANY years ago with the intention of shoving it on the web but never got around to doing so. However a friend to whom I sent a copy did put it on the web but that free site only lasted a couple of years but since then it has again been put on the web and below is one small section which might amuse although if you have already assembled the motor I suspect it will NOT amuse. IF you want to read the rest of the 'epistle' and as you have fitted to your bike a slipping dragging and ridiculously heavy to operate joke for a clutch you may very well wish to do so. It can be found on
http://a20b767e.magix.net/#xl_xr_page_1 but a few errors have somehow crept in and one section is totally missing so if I live long enough and find the required enthusiasm I may get the friend responsible to correct it but do not count on it especially the my living long enough bit.......
The missing Dominator camshaft oil bath.
Decades ago I took a friends old vintage race (championship?) winning 77 motor apart. It had stood on his garage floor for years with the crankcase drain / oil ‘strainer’ removed. Put it on the bench and thought I would amuse myself before going home by removing the head and barrel just to see how many cam lobes were missing. Turning the crank and cam over to my total amazement not only did all the lobes look to be in perfect condition but all were coated in oil. Having NEVER witnessed either occur before it was such a shock I stayed on to investigate which revealed that the cam ran within an oil retaining oil bath that had still been full of oil which the rotating cam lobes had dipped into and as the metalwork was part of the original crankcase casting I naturally wondered if it was an original design feature and whether its non-existence on later motors had something to do with the cam (and follower) premature failure problems they were / are often prone (being very polite) to suffering from. I wrote to Mr Hopwood asking the question and in his written reply he stated it was an original design feature with the lip of the oil bath designed to run within 1/8 to 3/32 inch of the flywheel rim to pick up oil from it. It would of course also retain the oil passing the followers from the head. When Mr Hopwood and others designed the Dominator engine in the late 1940s they knew that to avoid premature failure of the cam and followers good lubrication is required especially during the engine start-up period before any oil gets flung about in the crankcases from the big ends etc and especially when the cam was at the front of the motor. Triumph twin exhaust cams at the front were usually the ones to fail, most of the oil flung off the crank having lubricated the inlet cam at the rear and the bores.(Wonder if that is one reason why BSA twins were designed with the cam at the rear?). MUCH later I noticed my old Piper Cams tuning book states that in their experience most cams that fail prematurely start to do so during the engine start-up period due to incorrect lubrication with many starting the process to premature failure even before the engine is actually fired up due to people assembling the cam and followers dry and then turning the engine over with full valve spring load being applied resulting in ‘galling’ taking place between a cam and its follower and that once this has occurred premature failure is assured. Guess what engine build lube / grease or thick EP140 oil is for and why one should ‘charge’ the Norton crank with oil before first starting a new / rebuilt motor. The Piper Cams book lists a few other causes such as fitting old non reground followers to a new cam or vice-versa or when rebuilding a motor using the same cam and followers but not ensuring each cam lobe is matched to its original follower. So, Mr Hopwood and co included an oil retaining camshaft oil bath in the original Dominator crankcases to RETAIN the oil returning down from the head via the cam followers and from the lip running 1/8 – 3/32 inch from the flywheel rim picking up oil from it. At the Norton factory I assume (incorrectly?) that before a motor was first fired up or as a motor was installed in a frame someone poured some oil through a removed exhaust tappet cover to fill the oil bath so the cam was correctly lubricated when the motor was first fired up and when an owner fired up his early model Dominator the next day, month or even year after last using the bike the lobes of the cam instantly dipped into the retained oil supplying the lubrication required between the cam and followers. It was not rocket science, just good Engineering and very cheap to include at the original design stage. Funny how cams never seemed to give any problems on early motors…….
UNFORTUNATELY from probably that point on, with every new version of crankcase pattern made, the oil bath lip reduced - as did its oil retaining capacity – until, by the time of the 99/650 and Atlas, it had just about been eliminated. Tilting the Atlas engine forward for the Atlas Mk3 (Commando) may possibly have helped a bit (but I doubt it) and from that point on every new edition of Commando crankcase continued to remove it even more till it finally no longer existed leaving just a big lump of useless alloy beneath the cam and, funnily enough, camshaft premature failure was not exactly uncommon on later Dominators and Commandos - especially if your Commando motor was fitted with one of the incorrectly hardened cams Norton at one time produced! I still have a new one and its original Norton ‘genuine spares’ wrapping somewhere in my loft.... 350 Vickers surface hardness / softness, the new 4S one on a book (?) shelf behind me giving a hardness of 626 Vickers.Of course things were not helped by we younger owners thinking a higher lift racing cam would make our road bikes faster but which normally had little or no effect or even slowed them down as very few ever changed the inlet or exhaust lengths to tune them to the new cam or set up the carburation to suit or even set up the valve springs so they didn’t become very close to or even become coil bound at full lift increasing the load on the cam lobes and followers - mainly because we knew very little or nothing about such things. One friend recently told me that his new standard 650SS was timed at 118mph but that after putting all the go faster mods into the motor it only made 110mph and that the tuning modifications were quickly removed! Luckily he had not had big ports and valves fitted which would have probably slowed it down further with the reduction in gas speed…….To get these higher lift cams to fit in the crankcases WE followed the instructions shown for example in the Dunstall tuning book which shows a picture of someone attacking what was left of the oil bath with a rotary file so the higher lift cam fitted the ‘tunnel’ probably reducing the oil retaining capacity even further….. If there was any to start with. My Dunstall’s ‘tuning’ book makes no mention of the camshaft oil bath design and its purpose nor have I seen it mentioned in any other Norton ‘tuning’ books so I assume the writers were unaware of it and its purpose just as they apparently were at AMC and NVT. The Dunstall race cams as the one shown in the Dunstall book (as per the earlier Mr Hele works Domiracer motors) had a pressure fed oil supply exiting through a hole in each cam, as did the cams in the Geoff Monty / Dudley Ward Triumph engined ‘Monard’ race bikes which were ridden by the likes of the late Bill Ivy. (Remember his TT 100 plus mph lap on the 125cc Yam? Didn’t he stop at ‘The Creg’ to ask who was leading and following team orders let Phil Read through to win?). Spent a few weekends in my younger days (trying to learn) staying with the Gent (and his family) who drilled the ‘Monard’ cams along with manufacturing the gear oil pumps and new timing covers that they employed. Wonder if the new Norton motors have a cam shaft oil bath or positive lubrication to the cam? Not that many owners will I suspect actually ride them very far. When Rotary Norton announced they were closing many bikes with only a few miles on the clocks were shipped in for a service so they had clearly been bought as toys to look at or investments rather than as bikes to actually ride.
I’ll bet few people know the percentage of Triumph 650 unit engine exhaust cams that, due to lack of lubrication in the front of the crankcases, were changed under warranty at one time. I heard from a factory service Gentleman it was over 25%. Wonder how much that cost Triumph? Probably not as much as changing main bearings on Commandos all round the World along with those in every engine in the production system cost Norton! Triumph management eventually, so I heard, listened to people within the company who knew a bit about Engineering and agreed to have their cams nitrided making them even harder and more wear resistant. Having had people spend lots of time and effort at Triumph trying to sort out the cam and follower lubrication problem with numerous different modifications to the oiling over the years I guess the only thing left to do was to nitride the cams or install camshaft oil baths front and rear and nitriding was the cheaper and easier option…! I note that later T150 or T160 motors had a timed oil pressure feed to all followers / cams but when I enquired as to how well the system worked WAS TOLD it was quickly removed as it reduced the amount of oil available to the crank and if correct clearly ‘lots’ of testing had been done before introducing that modification! Wonder if the 6 start Norton oil pump gears were simply a bodge introduced by Mr Hele to allow for the extra oil required to feed the Domiracer cam shaft rather than redesigning the existing pump? I really must chivvy up the friend I tasked to find out for me by asking a Gentleman who worked with Mr Hele on the Domiracer motors.