soft cam

Yes PW3 cams are chilled cast iron. Same material as GM cams. I have seen no wear problems yet.

Of coarse the chilled cast iron cams used in GM cars failed regularly in the late 70s. Remember the early 350 GM diesels. They broke down the oil quickly and cam failure was the result. One of my regular customers used Amsoil in his new diesel [in 78] and never had cam problems. Just injection pump problems.

I don't know what the material is in the soft MK3 cams but personally I wouldn't worry about the cam hardness. Use good lube and I think any of them would be fine. If the lube breaks down I don't think it would matter if the cam was hard or not after a few minutes.

Of course if I had a choice of two cams laying there I would likely pick the harder one.

I recently rebuilt a friends 850 MK3 with very high mileage. It still had the stock cam in it and it looked good. It tested at 42RC which is what I have found was about average for that cam. We re-installed it for another go around. Jim

A couple of years ago I had a conversation with the owner of Web Cams. She definitely recommended NOT running Mobil 1 in our Nortons. Her recommendation was an oil with a high zinc content. Toroco MPZ is a favorite of mine.

The zinc advantage is for no oil pressure start ups and combines with the phosphorous to from 'nano pads' on steel surfaces but only if local oil temps get over 100'C-200+F or don't form and same as oil w/o enough. Pads wear off on starts and must reform before shut down. Not good to start up and not let reach full temp before shut down and slow idle ain't going to heat oil enough while minimal oil wedge in rod ends. (zinc dialkyldithiophosphate a.k.a. ZDDP)

Yes I have spoke to the same woman at Web-Cam. But I have been using Mobil 1 and recommending it to my customers for many years with excellent results. I have never had a cam failure with Mobil 1 in all of my bikes. The spec page for Mobil 1 shows higher zinc content than most in their 15-50 extended range which I used for many years but is no longer available [emissions] and even higher in their 20-50 V-twin oil which is what I use now. The light duty Mobil 1 oils have had low zinc for some time and that may be where she got her info.

All of the newer oils that are approved for use in emission control cars have low metals content to avoid fouling the convertor and I certainly would not recommend any of those for a Norton but most motorcycle specific or HD truck oils still contain the additives we need. Jim

I guess there are recommendations, and then there are recommendations. If Jim Comstock recommends Mobil 1, I'd take that to the bank.

I am sure there are other oils that will do just as well as Mobil 1 . The one thing that keeps me using it is the fact that it is available at just about any auto or bike parts store so when I am away from home I don't have to go searching. Jim

comnoz said:

Yes PW3 cams are chilled cast iron. Same material as GM cams. I have seen no wear problems yet.

Of coarse the chilled cast iron cams used in GM cars failed regularly in the late 70s. Remember the early 350 GM diesels. They broke down the oil quickly and cam failure was the result. One of my regular customers used Amsoil in his new diesel [in 78] and never had cam problems. Just injection pump problems.

I don't know what the material is in the soft MK3 cams but personally I wouldn't worry about the cam hardness. Use good lube and I think any of them would be fine. If the lube breaks down I don't think it would matter if the cam was hard or not after a few minutes.

Of course if I had a choice of two cams laying there I would likely pick the harder one.

I recently rebuilt a friends 850 MK3 with very high mileage. It still had the stock cam in it and it looked good. It tested at 42RC which is what I have found was about average for that cam. We re-installed it for another go around. Jim

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I did my masters thesis on piston ring and liner wear so I do know that I know very little about the subject.... There are so many variables involved and the hardness of each of the wear surfaces is definitely not the be all and end all of the situation. Cams and followers will quite regularly run in a boundary layer regime and the oil becomes very important (as long as the contact stress isnt too great), in the case of two strokes which I was looking at the oils had a bigger influence (if you only consider reasonable material couples eg no titanium) than other variables.

I did my masters thesis on piston ring and liner wear so I do know that I know very little about the subject.... There are so many variables involved and the hardness of each of the wear surfaces is definitely not the be all and end all of the situation. Cams and followers will quite regularly run in a boundary layer regime and the oil becomes very important (as long as the contact stress isnt too great), in the case of two strokes which I was looking at the oils had a bigger influence (if you only consider reasonable material couples eg no titanium) than other variables.[/quote]

I am sure that is right. I have always been told that the best wear between two metals occurred when one metal was very hard like the stellite pad on a lifter and the other part was much softer. Not sure that this applies to a cam but it does in most sliding applications.
I always figured that the harder cam might show some advantage at slow speed where the oil may not be able to keep the two parts from contact but I really don't know. Jim

comnoz said:

GRM 450 said:

Hello Jim,
Did the soft Mk3 cam have a "P" stamped in the end?
Mine did and I tried to find out what the "P" meant. I think it was Nick from Andover??? said it meant Parkerised? (don't quote me on Andover as I asked questions every where and this was the only answer I recieved)
I looked up Parkerised and it is a coating put on guns etc to stop rusting and look nice.
Can't see why anyone would be concerned about a cam rusting or looking nice when it lives in the oily black innards of an engine.
It was very soft also.

Graeme

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Yes it is stamped P. and still has that black coated look. Parkerizing leaves a very thin hard coating but doesn't last very long. Jim

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It's not to do with hardness but start up lubrication, part of the process etches the cam, phophate coating and a molybdenum disulphide coating, Helps hold luberacation on initial start up.

Why is it every time I come accross a problem on one of my Commandos somebody somewhere is going through the same hassle, pic taken of the cam on my Mk3 last week (still not had time to get the motor out) Bike has done about 12K miles but before I got it god knows how it was treated, I've put around 5K on it, regular oil changes etc but as I say previous owners maybe started the damage, just rebuilt a MK3 about 3 months ago with the same issue, deja vu or what!

excessive wear on high loaded surface's ,is due to long periods of standing .Oil drains away to leave dry surfaces. Most classic bikes are stood for weeks,even months/years?
It takes only a few dry turns to scuff the surface, poor crank case design ie No cam trough . Triumph 650 bonnies where the same.i have seen many scuffed cams.

Big problem is the oil system, How many Early Norton owners removed the oil tank cap and placed a finger over the return when freshly starting? otherwise it took minutes before the rockers got oiled :!:

My advise; after a long stand remove the rocker covers and tip in a cup of oil before starting :!:

Norton have a method to stop that John, it's called wet sumping, no dry starts,maybe the anti drain valve on mk111 works to well

I started researching this in the mid 90's when I bought my basket case MKIII 330046 with an engine that came with NO CAM and dead lifters. I put a $15 flea market 20M3S cam (hard) and never looked back. It's maiden voyage was at the INOA national rally in Hiawassi Georgia.

The research I did on cam hardness started and was published on the net over 10 years ago:
http://atlanticgreen.com/hscam.htm
At our local NENO club tech sessions. I had suggested the soft cam problem and 2 MKIII owners "felt" like they had no problem. After I convinced them it warranted a look..Well we split their motors and ....you guessed it JUNK cams that had started or were in cam mid self destruction.

I have diagnosed soft cams in MKIII"s for a long time and also predicted failures.

Also the jury is still out on the "new" iron cams that are being sold. One I bought for a customer, it cracked/split exactically on the mold part line.... in line with the first lobe. the factory finally warrantied it but I am not confident enough to use them any more. Oh yeah, this cam was replacing another diagnosed MKIII soft cam disintgrating cam.

True, the hardness of the cam is not an only cause for failure but I am so disheartened with MKIII cams that now in my NOS 6 mile unused MKIII commando, I am going to pull the motor and change the cam before I ruin this new motorcycle. ALL the MKIII cams I measure are LOW 20's

Also you will note from my data a very consistant semi softness in combat cams (30'sRC) that comnoz has not picked up on ....or not bothered to mention?

I am not going to "dis" anyones opinion on the subject, but for a long time I clearly done the actual research and have taken data. The basic cam design started in lats 1940's in an engine that had very much softer springs and lighter valves and gentler cam profiles.

Dave,
I know you have been testing cams a long time. I have wondered why your readings didn't agree with mine. Are you testing on the base circle of the cam. I have seen some very low readings there. Do you have a fixture to hold the cam on it's side under the penetrator?
Nearly all the cams I have tested have been used cams. Could work hardening on the face of the lobe be the reason for the difference in readings.

My machine is a Kentral motor driven tester. It has a recent diamond and has been calibrated. It has been very consistent with the specs on known new parts.

You are right in that I have not mentioned a semi-soft combat cam. I have not seen one. Not to say there could not be one.

Chilled iron cams are definitely brittle. I have seen cases of pulled threads but yours is the first time I have heard of one broken in normal use.

The only cam failures I have had on my own bikes was back in 1981. I had my MK 3 cam fail. And 3 months later the replacement [hard] cam failed.
After the second failure I started using BGMOA along with the valvoline car oil I had been using. It was an additive package for motor oil with lots of ZDDP and was recommended by an old engine guy I knew. Never had a failure since then. Jim

Jim
I had borrowed from work, an Ames tester model 4-2: http://www.amesportablehardnesstesters. ... models.cfm
Since then I bought my own of this same model, since I ocassionally test tooling that I make, then harden in my furnace.
I use an angled anvil to set the lobe in: http://www.amesportablehardnesstesters. ... sories.cfm.
After testing these things all over until they are pricked like a pin cusion, so I think the base circle reflects generally the overall hardness of the cam.
I HAVE tested, never installed, NEW old stock Norton 20M3S era cams, which are indicated on my web page.
850 73-early 74 cams should be generally OK. I have never ever had a hard 75 MKIII cam, but I have not tested them all :mrgreen:

A soft cam is not an automatic death sentence but I'd still go to great pains to find a hard one over a softie....and then use good oil

I just went out and did a quick test. Here is a used but very good factory 4S cam .

Testing the base circle I get 32RC



And testing the face of the lobe I get 59RC



Some of the difference may be due to the change in radius but obviously the base is softer on some of them. Jim

I'm sure you know this, there are charts available for compensating when measuring cylindrical surfaces, the compensation varies with the diameter. It's always an addition
though, so any number you initially read on a cylinder will be lower than the actual hardness.
One can obtain hardness standards to do a quickie calibration, they are the disks that are +/- 0.5 Rc. I use them first to check the instrument before checking anything.
Stop and think for a minute what is happening here.
If these, and I don't know if this is the case, are carburized in any manner or surfaced by plasma nitriding or any other type of process that may need finish grinding to remove process distortion then it is possible that the case thickness is unevenly reduced as the lobe is ground.
If this is an induction hardening material, again I haven't ever needed to know, it will still exhibit a cased structure and there is a possibility that the pyrometer was not correctly calibrated or aimed or some coils were not properly energized, or the quench was ineffective, etc.
My experience is that a case specification is meant to be that hard at a particular depth, harder at the extreme surface and softening toward the center or the deeper you go.
So it's understandable how the hardness will vary around the cam as the distortion is removed at finish grind.

splatt said:

Norton have a method to stop that John, it's called wet sumping, no dry starts,maybe the anti drain valve on mk111 works to well

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Good point, stick in a anti-sump valve and keep the crank case nice and empty of vital blood. Pehaps roller rockers are the answer :roll:

Yes I have a chart for radius. But if I consider the face of the lobe to be flat and use the diameter of the base circle it only increases the base hardness by 6 to 8 points. I suspect the work hardening of the used cam face may make some difference also. I don't know how much.

I do have a set of calibration disks.

Here's another thought,
if the case is unusually thin then the penetrator load will be too high and will provide an erroneous reading.
A proper section would be needed to analyze the case condition.
No matter really if poor oil is suspect.