This listing is for a matched pair of Inlet and Exhaust cam to fit the 350cc International SOHC engine - with the prothe of one of the most common profiles fitted to both Model 40 350cc International and 40M 350cc Racing Internationl - 64.66 (Inlet) and 63.89 (exhaust) cam profile. These cams are manufactured for us by a long established UK manufacturer to the original Norton (verniered) design. Each set comes with a useful fitting sheet.
Price is per pair.
Back in Stock Feb 2025 - We have just had a new batch of these cams in stock, from our original cam maker whom we have used for the laast 20 years.
Backgrond Information:
This profile is the standard International Norton SOHC 40M 64.66 and 63.89, which was fitted to both 350cc road International and post war 40M SOHC Manx models - They should also be suitable for early CS1's if you want a slightly lower profile than Inter cams.
There seems to be less informaton available on 350cc cam profiles than on the 500cc profiles - but in discussions over the years with other SOHC experts, it seems this profile was most commonly fitted to 350cc Model 40 International models from the late 1930s onwards, as well as the 40M Racing International or 350cc SOHC Manx models.
However, if you own an earlier (Arthur Carroll) CS1 (i.e. pre-International), or a later CS1 (i.e. SOHC with non downdraught inlet tract) - or just want a 'softer' touring 500cc engine - it has worth bearing in mind that information I had been told many years ago was that the 350cc cams (as shown here) are a possible alternative - having similar cam timings to the 500cc models but slightly less lift.
And of course it should be remembered - that due to the general competition design of this engine (which were more for speed than long touring distances) - the cams on these models often get a lot of wear, due to the high thrust - it is not unusual to strip an original cambox to find the original cams have much of their original profile highly worn!! (and if that is the case - dont forget to test valve to piston clearance as part of the valve timing process - if fitting new cams!
These cams are manufactured for us by a highly experienced UK company, who have been making these cams for us for over 20 years. They are to the original Norton pattern - which includes the original vernier holes, so that the inlet cam can be 'pegged' to the exhaust cam (which is statically located to the camshaft with a woodruff key) with a special roller, in various pre-defined positions in relation to each other, therefore allowing a slight variation of valve timing between inlet and exhaust cams. We supply an information sheet with each set of cams that helps explain this. Note: the special roller that locates the two cams to each other is sold seperately - Item 0054 and we recommend having a couple spare - as very easy to drop and lose one on the floor when fitting . . . I have done that a few times!.
As a final note on this engine and cam timing design - along with the vernier holes on the upper camshaft bevel gear - which allow slight variation of timing of both cams in combination - results in a very flexible and highly adjustable means of setting the valve timing - remembering of course, that back in the 1930s - this engine was designed primarily for competition. However, the relative complexity of that design (compared to other machines of the period), alongside the also necessary shimming process necessary for the vertical bevel gear design - means that assembling an engine for the first time can seem quite daunting - and sometimes take many attempts to get right!
My only advice to help with this would be to say - be patient and methodic, and dont be disheartened if it takes multiple attempts to get the shimming and valve timing correct - most of us are the same, and although you get more familiar with the task - it is never totally easy, but worth it in the end!
