soft cam

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The cams are listed as EN32B which crosses to SAE 1016 a case hardening steel...nitiriding should be ineffective....
I wasn't there at the factory in 74/75 but that's what I had heard happened to MKIII cams.
Probably just another myth... but their soft condition remains a real world condition that you can ignore or deal with.... :oops:
 
dynodave said:
The cams are listed as EN32B which crosses to SAE 1016 a case hardening steel...nitiriding should be ineffective....
I wasn't there at the factory in 74/75 but that's what I had heard happened to MKIII cams.
Probably just another myth... but their soft condition remains a real world condition that you can ignore or deal with.... :oops:

Do you know if the same material is specified in the MK3 cams as the earlier cams ? Jim
 
I bought my Combat Interstate new in '72. As with most of them the main bearings failed at about 4K miles. I agreed with my dealer & Norton that they would supply me with the parts so that me & a friend (who raced Norton twins successfully) could repair it ourselves. I didn't trust the dealers mechanic. When we got the engine apart the exhaust lobes on the cam were marked. We found out that since my bike was built Norton had started to have the cams Tuffrided, which I believe is a trade name for Nitridng process. I lived not too far from the factory & managed to find out where they were getting the cams Tuffrided. I had a drive down there one evening to have a look & discovered that they had an evening shift working. I just walked in with my cam in hand & asked if they could Tuffride it. They had a bin full of Norton cams. They did mine there & then for the price of a beer!

That SS cam lasted about 35K miles until both exhaust cams were well worn. I replaced it with a cam that a friend got from the factory in early '73. I didn't ask how he got it :roll:

That cam has now done about 20K miles. I used 20/50 mineral oil for about the first 25k miles I had the bike & things did wear out, e.g. had to replace valve guides at that mileage & needed a rebore soon after. I started to use straight grade 40 & it certainly slowed the wear rate in the engine. We can't get 20/50 Mobil 1 so I've never tried it but am happy to stick to Silkolene grade 40.

Ian
 
It seems like there are a lot of variables on the table here, right from measurement to materials...
Now the cast iron cams the hardness reading is probably pretty accurate, the steel cams could possibly give readings that are all over the place due to the case hardening (carburising in this instance). If the indent is close in diameter to the thickness of the hard case the readings could be low, if I was doing this I would try and do it with a Vikers micro hardness machine (yes ideal world, expensive etc etc), it will measure the case hardness more accurately than the Rockwell machine.

Now the difference in hardness around the lobe is interesting and may be a combination of a couple of things, firstly it may have more of the carburised layer ground off so the soft substrate will have an influence on the reading and secondly there may be strain hardening from loads while running. If there is strain hardening present it means that the cam (face) will have a defined fatigue life and will fail from subsurface cracking, this will show as pitting/spalling on the end of the lobe.
 
One point missed here; Influence of surface roughness on friction and wear,
Surface finnish and wear , make's all the differance to long life . Harden a "Rough" surface will produces a rasp like surface that tears away other bearing running on it.
super hi cam loads such as common rail injection pumps have precision lapped surface's , give them Norton cam finnish and they would'nt last 10 miles! It's not about hardness its about surface finnish. Trust me Im a doctor.
 
I suspect there may be several things that may have influenced the cam failures seen.
I modified a cam last night for roller bearing races which means I turned and ground the bearing races around 3mm. I noted the hardness on the unscrolled shaft was over .060 inch deep. It was a 2S cam. Don't know if it means anything. That cam checked at 65RC all the way around. Jim
 
I got 5 cores from Newman cams/GB where we ground our own profiles on for our 905 engine. They all tested to 52 HRC. The last dynorun was disappointing as the motor made 73 Nm at 4500 and did not improve at higher revs - it should have really come on song as the hottest cam was fitted. We teared the engine down and found some wear on the lobes and followers despite the oiljets in each lobe.... and contact marks to valve pocket in piston (left inlet/ right side exhaust) This is not realy possible as they all had enough clearance so all four pockets should have marks if valves were floating heavily - not only two as spring pressures were set exactly the same.
So we built a little testrig for the cam/valvetrain to test different followers, springs etc. This could be run on one of our milling machines up to 5000 revs (equals 10000 at crank)
When running the first (unused) cam it became clear that the valvetrain workes up to a certain speed as the noise of the moving parts was constantly and in rythm - from that point on another noise mixed in and not in rythm. Within 1 or 2 minutes we had the first wearmarks on the new cam so we knew for sure where the noise comes from.We used an adjustable strobelight to check all moving parts and found at 2000 (cam revs) and above that the followers get wedged in the cylinder tunnel due to the design of halfround parts that rub against each other and have too much overhang outside of the cylinder barrel and heavy sideloads from our fierce cams. This led to very high loadings on the cam/follower combo as everything else compressed until the follower overcame the friction and moved on. So the valve did not follow the cam lobe correctly... and as the lobe starts to lift the lifter almost at the outer edge of the Norton follower the cam has only 5 mm surface on the follower to start the valvelift - not very good for the already quite small and slim cam lobes that a Norton has.... We tried different spring loads, even tried original followers etc - it did not make a real difference. Now we are making followers to a different design that will give a full 13mm wide surface over the whole lift range. And these followers will have a sideload support surface to take all the sideloads from the follower. This new system will be tested again in the milling machine and if it works there it should work in the engine as well - keep fingers crossed.

Cheers

Hartmut
 
I have always used BSA followers when I ran a wild cam.
Are you using a radius ground lifter? Jim
 
nope - no radius - although I tried that on the test-rig. Didn´t help much. The followers that we will test in a little while are similar to BSA or Triumph but a bit bigger - the stem is 12mm, drilled for lightness and a cup pressed in, the foot is 13 x 34mm, drilled and slotted for lightness as well. So they should be much lighter than the std stuff (haven´t weighted one yet) and give adequate surface for our cams. Time will tell....
 
I wouldn't expect a radius ground lifter to help. They will create more side pressure on the lifter although if you are limited in lifter diameter a radius ground lifter may make a better cam profile possible. Jim
 
I hate to barge in on this highly scientific discussion, but have to say that in our road and race bikes the cam followers and cams have never been a problem. In the racers we run PW3 cams, on road bikes everything STD, 2S, rarely 4S (all supplied by Andover Norton), PW3 (supplied by Mick Hemmings). For racing we lighten the cam followers by machining bigger "windows" into them, and naturally lighten the rockers, too.
There was a problem on OE camshafts in the Mk3s and the cams made from the same cores until about the mid-1980s, in that the core material was too soft. So, even though the surface hardness was to spec, the pressures in the valve train acting onto the cam lobes via the cam followers would eventually shift the cam material UNDER the hardened surface, which led to the hardened surface having only air below (speaking very simply) and to the surface then cracking up.
After about 1985 new core material was used and the problem has since been history. Buying "New Old Stock" is not always a good idea!

Another thing worth checking is the machining of the tunnels for the cam followers in the cylinder barrel. We just had a customers engine in which needed new camshafts regularly. The reason was that the bores for the cam followers were not machined up far enough, so the cam followers could not go upwards far enough and destroyed the cam lobes regularly! The very patient customer had bought 4 camshafts over the years and never found out WHY the cams went. That machining mistake may have happened on more than one barrel over the years......... Just a thought.
Joe Seifert
 
Joe, I have always regarded the MK3 cam as suspicious and seen quite a few failures and have also seen a few that lasted a long time.

What I wonder about is the tales I have heard concerning soft early combat cams. I have seen a lot of them fail but the case hardening always looked pretty good from what I could tell. Any thoughts there. Jim
 
Well we will have a see what a "new" 6 mile unused MIII cam measures out too! As I said in a previous post I will be ripping the cam out of my MKIII # 333906 which shows 00005 miles and has never been on the road/registered.

Joe...are your lifters more or less cut/modified than the dunstall modified lifters shown on my site?
http://atlanticgreen.com/images/dalift.jpg
all four lifters were cracked between the slot and the hole....I was somewhat surprised since the actual cam was so mild...

As a noteworthy observation....my combat 202206 bottom end that had not been previously split, had a cam that was bent...yes bent. So when I went to the Shenstone factory in the late 80's I picked up a new one. That was the trip where Pete Kogut and I interviewed Leroux for the INOA Norton News article. I got to ride the shop mule rotary...loved it.

Most of my early views of MKIII's were from a guy in our local NENO club who was the original owner of his bike and went on to put 160,000 miles (by 1997) until his superblends finally gave up. I helped him split the crank only to find the sludge trap cleaner than an early nonfilter bike with 10K. He did have trouble keeping stock cams in it... no hot rod, only touring and long distance riding.
 
Dave, I have a pair of lifters just like the ones in your picture except one of mine is in two pieces. It was on a 2S cam many years ago. Jim
 
comnoz said:
What I wonder about is the tales I have heard concerning soft early combat cams. I have seen a lot of them fail but the case hardening always looked pretty good from what I could tell. Any thoughts there. Jim[/quote

That is more than likly a poor profile
 
What about nitriding as done to crankshafts and such. Polished up of course.
There is micro polishing services but don't know if worth it or not in lifters/cam.
 
Hello Gino,
Happy wrenching tomorrow! No known problems with our cams, just check your tappets are moving up freely far enough.......

As for the lightened cam followers (http://atlanticgreen.com/images/dalift.jpg) from memory I think ours aren't quite so radical as the Atlantic Green ones but don't have any pictures- they have been in our race engine for about a decade and as long as that is going well they are not coming out just for a photograph!

The Triumph Type camfollowers (http://www.norvilmotorcycle.co.uk/067799.htm) are an old idea going back to the 1960s. Being radiused you want to re-calculate your valve timing carefully and see where it gets you.

Joe Seifert
 
I did not expect that our homemade lifters would give problems. But after a quick check on the valvedrive rig with an ordinary 2S cam we had no problems up to 4000 (8000 at crank). So the problem seems to be generated by the much faster acceleration and bigger lift of our homemade cams. The valves have only 7mm stems (inlet/exhaust) and thinner valveheads as well. Pushrods are STD but rockers are lightened so weight is not an issue. The 320 degr cam might be a bit over the top as the engine coughed a bit up to 2000 revs as the charge was riched very much by blowback - the fog behind the carb disappeared at about 2500. Maybe I can cure that with longer inlet tracks...

I had several cams casehardened in the past after grinding my own profiles - never had a problem so far. I do have a cam in the shelf (might be a Megacycle - I don´t know) which did not respond to case hardening. Everything on the cam went black and hard - EXCEPT the lobes!!! They stayed shiny yellow - looks like stainless steel. They are still soft, could be machined with a file! So this cam must have been made by friction welding different materials ... I didn´t dare to put it in an engine but maybe the comparatively soft cam might work good with a very hard follower.....
Any thoughts on this????
 
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