Camshaft material

In a previous Roadholder I did see 'superior' big end bolts listed which had cut rather than rolled threads. Not superior in my book. EN40B would be perfectly acceptable for Dominator engines which have the camshafts sitting in an oil trough. Maybe not quite so suitable for Commandos which don't have the oil trough and where an an anti-drain valve fitted. At least they are available. Remember the Commando unhardened camshaft saga?

Gordon.

EN40B Could also be translated to - easier to work and fabricate less expensive material procurement and tooling needed = maximum profit!!

God forbid that I should find a good word to say for the advertiser in question,but even he deserves fairness of treatment.

Cast iron is a suitable material for low cost mass production of camshafts for low stressed camshafts. The chilling gives a hard white iron layer on the surface which is relatively wear resistant.

For small volume production and for high performance engines camshafts manufacture from steel billet is preferable. Accurate manufacture by CNC grinding machines allows for the production of a superior product,allbeit at a higher cost.

In both cases,cast iron and steel, careful control of chilling or heat treatment is essential as is the difference in hardness between cam and follower.

The cam/follower interface is the most highly stressed part of the engine. With chilled cast iron, the tensile stresses caused by the cyclic loading experienced at the interface and/or by lack of rigidtry in the camshaft can cause sub-surface cracking which, when a grain boundary in the structure, cause lumps to fall out (pitting). heat treated steel does not suffer this problem because of its higher tensile strength.

Ther are many pitfalls waiting for the maker of steel cams, the induction hardening process for steel camshafts must be carefully controlled, I know of at at least one manufacture who found that he was getting lots of warranty claims on new cars soon after delivery.

We found that the cam hardness varied greatly along the cam shaft and showed them that this was a result of the induction hardening and quenching process. We also supplied a special cam lubricant to help them while they got their heat treatment right.

Flatness of the cam in the transverse direction is also a cause of problems. I chaired the working group which developed the valve train scuffing test which is used in the ACEA engine oil approval system. This uses a Peugeot engine and we found that, using the'good' reference oil, we could get failing results for cam wear and scuffing on some cam lobes and followers and good passing results on others. Careful measurements showed that inaccuracies in grinding lead to slopes across some lobes such that the oil was squeezed out of the side of the contact causing starved lubrication and scuffing. Peugeot installed a state of the art cam grinder and produced 1000 perfect cams. The problem went away.

Provided the advertisers steel cams are similarly produced, then his claim is probably justified.

I agree with you on the general point that many people will find chilled cast iron cams perfectly adequate for their twins. However the correspondance in 'Roadholder' and other magazines strongly suggests that many aftermarket CCI cams are not satisfactory. It is probably easier to small batch produce Steel cams to a high quality than it is CCI ones.

The price doesn't seem out of line with other suppliers

Modern engines normally have roller cam followers. Old engines like ours have cam trains which are subject to sliding forces which can produce scuffing with the wrong grade of lubricant. ZDDP in classic oils is quite effective in preventing this. The newer grades of oils are lacking this additive as it contaminates catalytic exhausts. Our cams and followers have a hardlife and any componenet deficiency becomes apparent very quickly.

Can we please settle this question of modern oils not giving proper protection against scuffing because of reduced Zinc di-alkyl dithio phoshate concentration in oils because of catalyst compatability.

Scuffing wear is the principle mode of failure in cam/ follower valve trains.

Modern oils are available with ' normal 'levels of ZDDPs, these are the ACEA A series oils. Those which are formulated to meet ACEA C specifications have reduced levels of ZDDP but must meet exactly the same performance levels in the Peugeot TU3 engine wear test which is the standard industry test for valve train scuffing wear.

It seems that at least one supplier of classic oils is guilty of being ecconomical with the actuallity!

Do the results of ateston a Peugeot engine correlate directly to a Norton engine? Discuss. Of course we could end the discussion by fitting Peugeot engines to our Nortons - it has been done before!

The Peugeot engine is a single oHC cam engine with some differences from a Commando!

I had understood that it was engines with flat tappets such as air cooled BMWs , VWs, Nortons and Porches that have excessive cam/follower wear with modern oils with catalytic converter friendly additive pckages rather than ZDDP.

in the airhead world there has been a problem with some BMW sold 336 camshafts, that were wrongly ground, without a taper, a similar to the problem with Peugeot cams above,

In reply to Gordon,

in a word,yes. To the best of my knowledge Norton and other UK manufacturers never had their own specicifications for lubricants but recommended oils which met specifications based on general industry standards, SA,SB....SE SF etc depending on what was current at the time. These products passed tests run in a variety of car engines on test beds.

When we developed the PSA TU3 test for ACEA we correlated with 36 other engine tests then used by a variety of engine manufacturers. These had all sorts of valve train designs and metallurgies.

There is nothing odd about the Norton valve train, we have sliding contact and normal materials and the loads are unexceptional.

Technical comments can be driven by self-interest.Simon's valid observation: "I'm still waiting for my 'inferior' PW3 cam to wear out after 43,500 miles" speaks for itself. So do the Genuine Norton Factory Part cams Andover Norton sell, made in the same material and by the same process.Then again, not everybody gets supplied by Andover Norton and, therefore, has to find "alternative" sources and come up with reasons why the real deal is not on offer.The same goes for cut threads insteasd of rolled etc., etc.

Quite amusing, really, unless one gets landed with "improved" parts.

Funny how no one is apparently aware that when Mr Hopwood and co designed the Norton twin way back in the late 1940s they knew a bit about how to correctly lubricate cams and to ensure the cam was CORRECTLY lubricated they designed into the crank cases a camshaft OIL BATH that retained oil within in it so that during the first few revs during the engine start up period the cam lobes instantly dipped into the retained oil thus supplying CORRECT lubrication between the cam and its follower long before oil was eventually thrown off of the crank.

QUOTE. Piper Camshaft Tuning Notes. Page 36. 'The cause of premature cam and tappet failure is metal to metal contact between the tappet and cam lobe. Should this contact occur due to lack of proper lubrication or excessively high pressure due to valve train interference shearing the oil film, galling will take place. When galling takes place, metal is transferred from the cam to the tappet or from the tappet to the cam in a process compatible to welding. Small areas (microscopic high spots present on all machined part become overheated due to friction and pressure and bond together, tearing sections loose from the tappet or cam lobe. These pieces of metal remain attached to the face of the of the tappet or cam lobe and create further overheating during the following revolutions of of the camshaft and lead to premature failure of the effected cam and tappet'.

Another quote which I cannot find says something like.......In our experience most cams that fail prematurely do so due to lack of lubrication during the engine start up period due to lack of correct lubrication between the cam and follower.

Another quote. Mr Hopwood in a letter to me dated 21st July 1981......'The camshaft tunnel of the Dominator was designed to retain as much oil as possible and in fact collected oil from the flywheel rim'. Later in the letter Mr Hopwood suggests how the oil bath design feature could be replaced and states that the lip of the oil bath should run witghin1/8 to 3/32 of the flywheel rim to pick up oil from it.

Many years ago a Triumph retired Service Manager told me that at one time Triumph were replacing under warranty something like 25% of all unit 650 exhaust cams due to lack of lubrication at the front of the motor..... the inlet cam at the rear being reasonably well lubricated once oil worked its way around the motor. Apparently eventually Triumph mismanagement listened to the remaining real Engineesr and bodged things by having the cams nitrided...I assume it was cheaper than to change things and installing correct lubrication.... Did not one of the 3s have a pressure fed system that sprayed oil between the cam and followers??? If memory is correct it was quickly removed as the oil feeding the cams reduced the oil available for crankshaft lubrication!!!! I assume no testing was done before introducing the system ?? I was told by a Gentleman who worked on the Domirace project that the 6 start oil pump gears were iintroduced simply to offset the oil that was pressure feeding the Domirace cams....Mr Geoff Monty / Dudly Ward on their Triumph engine MONARD Triumph race twins also had pressure oil feed to the cams along with the Norton type gear oil pump required to feed the cams and crank. The new oil pump and timing cover being manufactured by ex AMC race mechanic Tommy Mortimer who also drilled the cams.

Decades ago Mr Negus was showing me the first of the new crank cases made using the new patterns , the old patterns having been destroyed on the orders of mismanagement who believed they would never make such lumps ever again and very pretty it looked....I asked...So where is the camshaft oil bath Mr Hopwood designed into the Dominator engine to correctly lubricate the cam? I was later told they were not going to change the patterns to incorporate the oil bath......

Some people actually reinstall the camshaft oil bath to ensure their new cam and followers are correctly lubricated, especially during the engine start up period........Mind you I once saw a set of cases where some brain dead had left a gap between the cases so that any oil entering the oil bath from the crank and down the pushrod tunnel from the head would run out probably faster than it ran in thus NOT retaining any oil at all to lubricate things the next time the motor was initially fired up.....!!

If you look in the Dunstall Tuning Notes book there is a photo of some 'expert' attacking what remained of the oil bath with a rotary file to allow a new super doper(go slower) high lift cam to be installed and thus removing even more of what remained of the oil bath..........

An interesting exercise is to lay out all the various editions of crankcases manufactured over the decades and witness how with every new edition of crank cases the oil bath oil retaining capacity reduced till it was non existent!! Funny how later Dominators and all Commandos had a premature cam failure problem...NOT helped by those clever people at Norton producing a batch of soft cams...I still have one still with its GENUINE SPARES plastic bag...Surface hardness is around 350 Vickers. The new 4S cam still on the bookshelf behind me has a label attached saying 626Vickers.....Quality Control?? What's that???