camshaft good to go or replace?

I am are getting the motor pieces together o start reassembly, looks like a PO had it open at some point. the bearing shells on one connecting rod were flat, the other had a groove.

Question 1; the attached pictures show the cam. it shows wear. when measured, the lift is still between 0.317 -0.320. can it be put back in or is it on its way out? I am assuming this is still a norton chilled iron cam.

question 2; i can get the shop to do a rockwell hardness test, but how to do it on the nose of the cam and not cause damage?





wise words needed

I think form the looks of that lobe this one needs to be replaced. also how about a pic of the followers but my guess is that one also is in need of work.

850dunstall said:

Question 1; the attached pictures show the cam. it shows wear. when measured, the lift is still between 0.317 -0.320. can it be put back in or is it on its way out? I am assuming this is still a norton chilled iron cam.

wise words needed

Click to expand...

850dunstall said:

I am assuming this is still a norton chilled iron cam.

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The Factory Workshop Manual (for early 850s anyway) sez that the originally installed cams were STEEL = EN32B,
so if you have a chilled iron cam then its a later replacement.

Could presumeably be hardness tested on the side of the cam, so as not to destroy the working face.
Those pics don't look too encouraging....

Considering the amount of work involved in stripping and rebuilding a motor... the relatively low price of a cam... and your pictures... I'd say a new cam would be wise.

Call JS Jim Schmidt and see what he will do for you with that very good donor in your hands.\
Be sure to send along the tappets for a freshening.

" Be sure to send along the tappets for a freshening. "

+1 The tappets will definitely need refacing.

Check them over very carefully. If the cam was changed about 10 15 years ago there was batch of followers around at that time which would lose the stellite pad. Look to see if there is any oil seeping out from under the stellite. Try warming them a little and you may see it seeping out. And check for cracks etc under a magnifying glass. We found about 50 % of old followers were damaged in some way.

the lifters look okay, but was planning to reface them, this cam looks just the one that came out of my 74 850, so the material is whatever they used, i am not happy with the wear, but do not know if the cam/followers were ever changed.

what was the factory quoted lift?

confirm material

is there any way to confirm the material of the cam, whether chiller cast iron or as suggested en32b? and how are they hardened?

Material = EN of some sort, no visible cast marks so possibly an original cam.

Fast Eddie said:

Considering the amount of work involved in stripping and rebuilding a motor... the relatively low price of a cam... and your pictures... I'd say a new cam would be wise.

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++++++ 1+

Nah, that's not worn...

THIS is worn ..

Whilst I am certain someone will give me a bollocking for yet again raising the subject of THE MISSING NORTON TWIN CAMSHAFT OIL BATH here goes for the nth time in the last 30 odd year although why I ......
When in the late 1940s Mr Hopwood and crew designed the original Dominator engine they knew that if you shove a cam into the front of a motor most of the oil thrown off the flywheel lubricates the bores leaving very little for cam lubrication.(At one point over 25% of Triunph twins were having the exhaust cam at the front replaced under warrrenty.... so a Triumph Service Manager told me!! They ended up nitriding them to cure the problem) They were also fully aware that if you run a dry cam against a dry follower at engine start up galling takes place. For those who do not know what galling is use the web. Suggested reading is The Piper Engineering / Cams tuning notes book which states something like ...in our experience most cams that fail prematurely start to do so during the engine start up period due to lack of lubrication...
Thus to preserve the life of the camshaft Mr Hopwood and crew designed into the crankcases an oil RETAINING oil bath for the camshaft lobes to dip into the very first time the cam rotated at engine start thus providing the lubrication required to prevent galling taking place along with a better form of lubrication for the cam with the motor in use as the oil bath also collects oil coming down past the followers. It was NOT rocket science just good Engineering AND very cheap to incorporate at the initial design stage. In FACt Mr Hopwoods letter to me on the subject dated 21 July 1981 states and I quote ...' 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 he states tha lip was designed to run within 1/8 - 3/32 of the flywheel rim. If anyone is clever enough to find my e mail address and ask very slightly politely I will e mail back a copy...

UNFORTUNATELY once Mr Hopwwod and a few others fled Nortons as LOSS MAKING AMC closed the Birmingham Norton PROFIT MAKING factory down there were very few left who know much about Engineering (and even less later on!!)and with every new edition of crankcase manufactured (for which new patterns were required) they cleverly slowly designed OUT the oil bath a bit at a time till the only bit left was a big lump of useless alloy beneath the cam as in Mk3 cases..... funny how camshaft failures never seemed to occur with the old model 77 motors and it is really interesting to lay out various crankcase editions and note the slow demise of the oil bath.......and guess at which point cam failures became the norm NOT helped by shoving rediculous cams into the motors which required what was left of the oil bath to be removed to accomadate the higher lift cams....as someone is shown doing with a powered rotary burr in the Dunstall Tuning book!!! Mind you Mr Dunstalls race motors employed Mr Heles Domirace cams which had a pressure oil feed to all the lobes...which required the use of the 6 start worm on the oil pump so the crank maintained the required oil supply... In my young days in Engineering it was called a ramification.....
I have one friend who is in the 'business' of rebuilding peoples Nortons for road and race use along with manufacturing new lumps for them etc and IF a customer twists his arm hard enough he will replace into the crank cases the oil bath but with the higher lift cams its a bit of a pain and with the later 89mm throw cranks and bigger later rods one has to be carefull the the big end nuts clear the oil bath lip....I will NOT mention his name as he does not enjoy doing the modification.
I only noticed this subject when many decades ago deciding to look at the cam in a friends old vintage race motor that had been laying on his garage floor for years... I took the head and barrel off in one and turning the crank over to look at the lobes was amazed to see every lobe covered in oil AND looking perfect. I wondered if it was a design feature so wrote to Mr Hopwood asking the question..along with a few other questions.... If memory is correct the motor won a Vintage championship or two and had been sitting on his floor for several years with the big drain plug removed.
I have seen cases modified to include the oil bath but the idiot incorporating it had failed to mate the two halves together so I guess more oil escaped than was being retained!! Clearly some people are incapable of laqpping two surfaces together. Some of us spent months in apprentice training schools filing metal squares to fit into square holes which we also had to file out and both had to fit correctly!! These days I suspect the 6 months I spent in the training sachool (before being allowed onto the factory floor for another 4 1/2 years of often painful learning) would be regarded by the UK government as a full apprenticeship resulting in a skilled person!!
Personally I am suprised that some enterprising soul does not offer a service replacing the oil bath ...... When I asked Mr Negus as to where the oil bath was on the first off new crankcases made when Norton were at Shenstone He asked me to explain which I did and on a later visit I was told the patterns were not being corrected as it would cost toooo much money.........clearly they wanted the business of replacing camshafts!!!

" an oil RETAINING oil bath for the camshaft lobes to dip into the very first time the cam rotated at engine start thus providing the lubrication required to prevent galling taking place along with a better form of lubrication for the cam with the motor in use as the oil bath also collects oil coming down past the followers "

I always wondered about the use of the side stand. That is going to drain all the oil in the oil bath to the left hand side.

But in principle I completely agree. For the later engines and my race bike I pour some oil down the push rod tubes to cover the cams if the bike has been standing for a while. On the race bike after a week. Only takes a few minutes unless the tank is in the way.

I wonder IF in the Birmingham Norton factory after installing an engine in a frame someone removed an exhaust rocker cover and poured half a pint of oil in to fill the oil bath so the cam was correctly lubricated from the very first engine start??
Reinstalling an oil bath is not hard to do and with the cost of cams these days...... HINT. When milling out the oil bath only mill in the area of the cam lobes........on the timing side the machined front fixing stud nut area makes the cases rather thin........

maylar said:

Nah, that's not worn...

THIS is worn ..

Click to expand...

and i'll raise you two...

J. M. Leadbeater said:

Whilst I am certain someone will give me a bollocking for yet again raising the subject of THE MISSING NORTON TWIN CAMSHAFT OIL BATH here goes for the nth time in the last 30 odd year although why I ......

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that nice but since i have never seen the innerds of one of those old engines, please show me a picture of the proper oil bath, as a favour to all i think it should be as a separate posting or just PM me.

thanks

It’s reasonably easy to understand, the so called “oil bath” for the camshaft is nothing more than a raised ridge at the rear section of the camshaft, which is part of the crankcase. This is there to retain oil for the cam lobes to wash themselves in. You will not be able to see if unless you remove the barrels.

Here is a view of a late 750 crankcase. Still there.

a hole in the water lined with wood.....

Bob Z. said:

Here is a view of a late 750 crankcase. Still there.

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i can see that on my 850 case as well but from all the comments i sounds like this trough was deep / better formed and has gotten shallower with each generation... and this not enough, with all the worn camshafts.... so is it even possible to add a little more of a wall on the inside edge. I've been more focused on dealing with the bigger picture of the rebuild at this point than to try and re-engineer the cam trough.

im sending the cam followers of to Jim Comnoz to get faced, and will replacing the cam as well

the stories goes... that a boat is a hole in the water lined with wood into which you put money... this norton rebuild isn't far behind...

The problem with high wear factory cams is that the material just doesn't hold up well. Its very doubful that more oil will save it. The lobes need to be hardfaced and then ground. I am just starting on hardfacing cams myself so I can have some quality control and choose the best grinds, it gets labor intensive. The other problem is the flat stock lifters. Radiused lifters last much longer. The pointy cams for stock flat lifters are a high stress and high wear item - the sharp nose just basically wipes the oil off the lifter. Cams designed for radiused lifters have a rounder nose and the stress is spread out over a broader area - the oil can wedge between the cam and lifter surfaces instead of being scraped off. So unless you go with aftermarket radius lifter designs, you can expect to be replacing cams.