camshaft replacement

Having just removed the head and barrels from a 1974 MK11a, I've come across 2 loose valve guides (exhaust), 3mm of carbon on the pistons and one very round camshaft.
The cam lobe has worn away a good 4mm of its peak, leaving it almost round instead of oval.
What could cause this? It cannot be oil starvation as all the other lobes are perfect with very little wear.
The motor has only done 8000 miles since the previous owners rebuild.
Is it possible to replace the camshaft without splitting the cases, ( wishful thinking ).
Thanks
chris r

The cam probably failed because of poor oil quality. There is also always talk of poor cam hardening.

You will need to split the cases to replace it. Jim

I have NEVER found a hard MKIII cam. Most are soft around 17-21 RC.
I heard some of the last 74's were also not hardened, but I have very little sample data on "know" 74 cams and therefore little ability to hardness test them.
I
early cams usually test much higher some up to 58 RC

http://atlanticgreen.com/hscam.htm

I have never seen a MK3 cam that tests hard either. They are made of a different material that does not harden like the earlier cams.
PW3 cams also test very soft.

I also have MK3 cams that are approaching 100,000 miles without problems. Jim

If you want the cam to really last - get the hardened steel cam kit from JSmotorsport with the radiused lifters. No worries about wear thereafter because the cam nose is more rounded with the radiused lifter geometry. They also seem to run quieter with less tappet noise.

My pre-Ms Peel had like 40K miles on it then I rebuilt and got 6K life changing miles on her spanking sports bikes in turning tests and in opens over 130 only a few would dare catch up before next series of testers - till throttle stuck over rev cold engine - but rode up to 110 mph with Huge windscreen power loss to discover RH exht lobe of 2S cam flattened. Don't know when or why but didn't lack power till after the over rev event. Ms Peel rev'd up so hard so fast knocked my hand off throttle twice slapping me back a couple steps so think the hi rpm hit so fast no oil flow had reached head in time but the other lobes seemed fine. Mystery unless that one lobe missed surface hardening. Tried to have it repaired by expert who said too trashed to do it so left it with him for scrap metal. I've Trixie Combat apart now that could barely keep up with elite cycles straining crap out of her but cam and lifter look pristine. Cam out now to reseal engine but thinking good time to nitride+polish for longer term.

The cam followers, one is well worn but the others are ok. Is it ok to have these professionally machined to reduce the signs of wear.
They would need to be reduced by 1.5mm at the most, or have they to be replaced to match the new camshaft?
chris r

The later cams can be sketchy for sure re: lobe hardness. Am putting an early good 70 cam into my MK111 project as I know lobe hardening is much better. The original was feeling rough after my tear-down at 10.000 miles indicated.

blacklav said:

The cam followers, one is well worn but the others are ok. Is it ok to have these professionally machined to reduce the signs of wear.
They would need to be reduced by 1.5mm at the most, or have they to be replaced to match the new camshaft?
chris r

Click to expand...

I took mine to my local machinist who does valve grinding. The followers are tipped and you cannot take it down any further than the stellite tip. It takes a long time and costs money to do, but is an absolute must if one or more of the followers is damaged. Bear in mind that 1.5mm down on the followers is 1.5mm down on the pushrod side of the rockers multiplied by the rocker ratio, which is like 1.1:1 or something like that, means that the tappet adjusters need to move that much as well. That should not be too much, but it's wise to make sure the new contact geometry is okay (when you button up the engine).

As for the cam, I did much reading on here and found lots of contrary views. WEBCAM charges an arm and a leg for the cam regrind nowadays ($380, core must be workable, so if the end journals are scoured, you're looking to start paying some big money to swap out and ream the cam bushings). The 2S/4S cams are an option, but aren't that cheap either. Went megacycle as it can't be worse than stock (quality looks really good), and they have a LOT of neat options, and are ~$370 shipped for a new billet cam.

blacklav said:

Having just removed the head and barrels from a 1974 MK11a, I've come across 2 loose valve guides (exhaust), 3mm of carbon on the pistons and one very round camshaft.
The cam lobe has worn away a good 4mm of its peak, leaving it almost round instead of oval.
What could cause this? It cannot be oil starvation as all the other lobes are perfect with very little wear.
The motor has only done 8000 miles since the previous owners rebuild.
Is it possible to replace the camshaft without splitting the cases, ( wishful thinking ).
Thanks
chris r

Click to expand...

You have had the really useful responses already.....so forgive me...but you post is just so naive, and makes me feel really old, the first time I lifted 850 barrels to find a round cam was '76! Thankfully it wasn't mine!

But no one answered your follower (lifter) question. Yes, you could have them refaced, it is done too regain a flat surface (what you need) or give them a radius for use with very aggressive cams (not what you need).

But if you are pulling it all down and putting in a cam of choice, new followers are a good choice to go with it. However, as I recently discovered you will have to be prepared to fully inspect and hand finish new Andover Norton followers, for which it would be best to have a surface plate handy and suitable abrasives/tools. AN do advise on this in the packing.

Though I know some are put of by the need to do this I would still suggest AN are what you use, unless you follow the previous suggestion and go with a JSM cam kit, which is a whole new ball game, check Jim's website.

But a good standard cam and followers is going to be so much better than what you currently have.

cyclepsycho said:

If you want the cam to really last - get the hardened steel cam kit from JSmotorsport with the radiused lifters. No worries about wear thereafter because the cam nose is more rounded with the radiused lifter geometry. They also seem to run quieter with less tappet noise.

Click to expand...

Where would JS be getting a hardened steel cam. From what I have found all replacement cams for a Norton except the PW3 or the factory grinds are a weld up and grind?

When I rebuilt my motor many years ago I had to do the lifters as they had some wear on the surface of the lifters, I worked at a TEC college in the maitenance workshop as a T/A, we made up a jig to fit 2 lifters and then mounted them on a surface grinder and did a few light grind with lots of cooling fluid, worked like a treat and only took about 10 minets to do 2 lifters, they were like new when finished and with my standard cam built up with a 2S cam grind, I am still running the same lifters after all them years ago when I machined the lifters, I no longer work at the TEC college but still have the jig to do them if need so.

Ashley

Some people like megacycle and some don't....Their cams are new core with the grind of your choice. It is rumored that they would even make a stock grind to special order (i.e,not stocked)
I had gotten a AN iron cam for a friend. It split on the mold parting line from "being over tightened".
Well I got a new factory bolt and screwed it in (against the AA unit), that is on a real steel cam not a chilled iron cam....until I broke the bolt, about 14 ft/lbs by the torque wrench. Well the iron cam died the steel one lived.
OK how do I feel about MKIII unhardened cams.
On my new old stock 5 mile MKIII...never registered or ridden other than factory test. I am going to pull the motor and change the cam with a NOS 71 750 cam before I ride it.

Last time I asked....(some years ago) Les Emery still sold his norvil cams which are steel not iron.
I have his 2S on a domi core, 7S domi core, 4S and 7S for late commando They were all tested for hardness.
I guess it's been a while...they were only about $150 back then. :mrgreen:

I recondition my own lifters on my surface grinder, but be careful some times they are cracked on the stellite pad.

dynodave said:

Some people like megacycle and some don't....Their cams are new core with the grind of your choice. It is rumored that they would even make a stock grind to special order (i.e,not stocked)
I had gotten a AN iron cam for a friend. It split on the mold parting line from "being over tightened".
Well I got a new factory bolt and screwed it in (against the AA unit), that is on a real steel cam not a chilled iron cam....until I broke the bolt, about 14 ft/lbs by the torque wrench. Well the iron cam died the steel one lived.
OK how do I feel about MKIII unhardened cams.
On my new old stock 5 mile MKIII...never registered or ridden other than factory test. I am going to pull the motor and change the cam with a NOS 71 750 cam before I ride it.

Last time I asked....(some years ago) Les Emery still sold his norvil cams which are steel not iron.
I have his 2S on a domi core, 7S domi core, 4S and 7S for late commando They were all tested for hardness.
I guess it's been a while...they were only about $150 back then. :mrgreen:

I recondition my own lifters on my surface grinder, but be careful some times they are cracked on the stellite pad.

Click to expand...

I like the Megacycle cams also. But they are just a weldup on a new shaft. [billet core]

I would like to find someone who will do a hardened steel cam with a custom grind so I can do some roller followers. Rollers will not live on a weldup lobe [or an iron cam]. And the standard profiles that are available on a hardened steel cam are not suitable for a radius lifter.

Actually I have found someone who is willing to do a custom grind on a hardened cam but for just a couple of them the price was over my budget. [over 1000.00 each]
Webcam is also willing to grind a steel cam if I supply the blank and then take care of the hardening and straightening myself after they grind it. [so I could save a few dollars -if I don't pay myself]

My NOS Mk3 [many years ago] is still running on it's original cam. [and just about everything else] It's at 27,000 now. Jim

Hello Everyone
I am also having to replace a failed cam in my MK111 after less than a thousand miles. It was of the 'chilled iron' variety and it had severely worn both inlet lobes. I found the comment about some PW3 cams testing soft interesting as they are made from chilled iron. What is the optimum material/hardness for these cams. All the well known vendors here in the UK say that chilled iron is the dogs bollocks for these cams and i have just ordered another one (a standard one this time, i.e. not a performance cam like the failed one) I hope i have not wasted my money on it.
I have refaced the tappets ( lifters ) by diamond grinding them using a toolpost grinder in my lathe
This shows the lathe setup, the tappets are held in close fitting thin walled tube in the lathes chuck


You can just see the tappet face behind the wheel

The end result, i will be hand fettling to remove the sharp edge on the tappet as i do not want this scraping the lubricant off the cam.
In the local NOC one of the members also has had cam problems with his MK111 and interestingly he now lets his engine wet sump so the cam is slathered in oil as soon as the crank rotates.

I wish there was more space available in the tappet (lifter)tunnel to redesign the tappets to a rotating type like the vast majority of engines. This would need a new barrel casting (bigger/different tappet tunnel arrangement) most likley new crankcases to accommodate
the new barrel design, new cam to provide wider cam spacing, new head design because of the wider pushrod spacing.etc etc A completely new engine in other words
On a slightly different note does anyone know the whereabouts of any Merlin Engineering Double overhead cam 8 valve heads that where made in the late 70,s early 80,s ? I have somewhere a Motor cycle weekly newspaper article picturing the said head fitted to a grasstracking outfit. I think it said it produced upto 90 h.p.

Ride safe
Peter Shand

The chilled iron PW3 cams measure around 40RC when they are new. Since they are cast iron they work harden quickly in use and create a hard wear surface. They are usually pretty good as far as lobe wear although the threads are a bit weak and the bearing journals wear a little more rapidly.

What kind of oil are you using? Were the lifters were properly surfaced with the failed cam? Was it broken in right and has the idle been kept over 1000 rpm? [Slower idle is pretty tough on a Norton cam]

Hello Jim
Thanks for the prompt reply, I was using a straight HD40 monograde oil. The lifters (tappets over here!) were brand new from Norman White.
Cam and lifters assembled with graphogen assembly compound (Norman whites recommendation). Idle around 1000 rpm (as far as i could tell!) and ridden fairly steadily for the first 50 miles or so.
Not wanting to start another oil thread but what oil do you run your MKIII on?
The lifters i have refaced were the ones removed when i replaced the cam.
What in your opinion would be the ideal material for commando cams?
and why is a slow idle not good for these cams?
Regards
Peter

dobba99 said:

Hello Jim
Thanks for the prompt reply, I was using a straight HD40 monograde oil. The lifters (tappets over here!) were brand new from Norman White.
Cam and lifters assembled with graphogen assembly compound (Norman whites recommendation). Idle around 1000 rpm (as far as i could tell!) and ridden fairly steadily for the first 50 miles or so.
Not wanting to start another oil thread but what oil do you run your MKIII on?
The lifters i have refaced were the ones removed when i replaced the cam.
What in your opinion would be the ideal material for commando cams?
and why is a slow idle not good for these cams?
Regards
Peter

Click to expand...

HD monograde oil would usually be good as long as it is not oil that is designed for automobile use. Newer cars use roller tappets and catalytic convertors. Automobile oils have had the extreme pressure lubricants removed from them to prevent fouling the convertors and they are not needed with roller tappets.

Most motorcycle oils and heavy duty truck oils still contain the needed additives for flat tappets. [zinc phosphate] You can often check the website for your oil and see what the zinc phosphate level is. I would recommend at least 1000ppm for flat tappets.

I use Mobil 1 20-50 v-twin oil but there are several oils that will do the job.

I prefer a hardened steel cam -they are the most forgiving to abuse. They are not usually available in different grinds as production in small quantities is price prohibitive.

A weld-up cam is just as good with flat tappets and is what I use as they are readily available in any grind you could want.

I am not a big fan of iron cams.

A slow idle will not create enough surface speed to float the tappet above the cam lobe on a hydrodynamic wedge. Engines with small diameter cams [like a Norton] need to turn faster to create the necessary surface speed. Jim

comnoz said:

cyclepsycho said:

If you want the cam to really last - get the hardened steel cam kit from JSmotorsport with the radiused lifters. No worries about wear thereafter because the cam nose is more rounded with the radiused lifter geometry. They also seem to run quieter with less tappet noise.

Click to expand...

Where would JS be getting a hardened steel cam. From what I have found all replacement cams for a Norton except the PW3 or the factory grinds are a weld up and grind?

Click to expand...

They are new (not re-ground) steel billet cams (not cast iron so they won't break) with hardfaced welding on the lobes.

Jim S

jseng1 said:

comnoz said:

cyclepsycho said:

If you want the cam to really last - get the hardened steel cam kit from JSmotorsport with the radiused lifters. No worries about wear thereafter because the cam nose is more rounded with the radiused lifter geometry. They also seem to run quieter with less tappet noise.

Click to expand...

Where would JS be getting a hardened steel cam. From what I have found all replacement cams for a Norton except the PW3 or the factory grinds are a weld up and grind?

Click to expand...

They are new (not re-ground) steel billet cams (not cast iron so they won't break) with hardfaced welding on the lobes.

Jim S

Click to expand...

Darn,
but that is what I figured as I think I have talked to every cam builder in the US to see about the possibility of a hardened steel cam and they all said no unless I wanted to order large quantities. Jim