I am trying to source 4 x new (preferably old stock) cam followers / tappets (part number 20871) for my Navigator engine rebuild. Sadly the NOC shop is out of stock and having contacted the spares team a couple of months ago they told me they are trying to identify a suitable manufacturer who is willing to produce a cost effective production run. This of course is taking time, in part because of Covid.
I have therefore advertised in the Club Wanted classified section and searched Norvil's catalogue which doesn't even list them.
Does anyone know of a source of new Cam Followers or have a set of 4 new ones they are willing to sell me?
My understanding is the shafts and faces are hard chromed and then ground to the correct dimensions - does anyone know of an engineering company who can be trusted to recondition Lightweight Cam Followers as another option?
Finally, if you are in the same position I believe it helps raise the the priority of funding spares manufacture if you contact the spares team so they can gauge what the demand is to justify expenditure of club funds. Please add your name to mine!
Wishing you all a happier, healthier, more peaceful and prosperous New Year.
I cannot help with the parts you need but the proper process to follow so 'the spares team can gauge what the demand is to justify expenditure of club funds' is to complete the form -
Actually, if you look in the parts commissioning forum, you will see that someone has already started this thread. But it looks at the moment as no-one else wants the same part. We need numbers to justify making parts. So please add to the thread.
Thank you so much for the advice - I have searched high and low for the process to do this and completely missed the forum right at the bottom of the page! I have filled the form in and emailed it off and I will add my details to the thread! Hopefully others will see your advice and do the same - I can't believe I'm the only one out there needing new Cam Followers / Tappets!
Thanks again, Nick
I've been looking for these as well. Not sure I need them, haven't got that fat in to the engine yet.
I understand the followers are a source of noise and can wear prematurely. If new followers were to be made would they be the same as original or would it be possible to "improve" them?
Would anyone care to invest either some time or money to investigate if:-
The Navigator followers are 11.1mm diameter (0.4360" - 0.4365"), and this seems a strange number to be a random selection.
For the sake of £12.50 + £6.95 delivery, it may be worth a punt.
If anyone should have the dimensions of the Ford Kent follower, then I can compare to the Navi ones.
Hi Tony , I am using the Kent followers on my Navigator engine rebuild . They are 0.440 ins shorter than the original , but dimensionally almost identical otherwise and are manufactured to a good standard . I have manufactured new longer pushrod shafts from an aircraft grade aluminium . ( Dural ally no longer available ) The original pushrod ends can be removed and transferred to the longer shafts . I tried different methods to pull them off including using the freezer ,heat , and in some cases , brute force . Some came easily whilst others required the use of my lathe and drilling out . I have fitted new cam follower bushes ( from the club ) to the barrel and set them 0.125 ins lower than the originals . This is to ensure the shaft of the followers reciprocates within the working length of the bush . I also had a set of 4 original followers which had worn “ barrel “ shaped Centre less ground by a specialist grinding company . I instructed them to remove the absolute minimum to bring them back to parallel which resulted in a finished dia at 0.427 ins . (Minus 0.010 ins and only cost £30 ) This ensured the case hardening was not compromised as most casehardening tends to be around 0.025 ins deep .I intended to manufacture new bushes to complement these followers , but decided to use the Kent followers instead .
I've just taken a tappet bush (20751) out of a spare Navigator cylinder, didn't realise they were that short, 1.375". I suspect it may be difficult to make them substantially longer but it may well be possible to get a small increase in length. It does seem to be a poor feature of the engine, would be nice to do something about it.
Its been suggested that tappet bushes don't suffer as much wear as the follower. The cylinder I removed the bush from is on standard bore with almost no wear, 0.0015" max. (Shame about the corrosion!). The bushes are very "bell-mouthed", 0.005" wear typically. This would contradict the accepted wisdom and reinforce the point that the bushes are too short.
The bushes have drain grooves in the bore, any reason why they shouldn't be on the outside of the bush?
Although using a "foreign" follower may be a low cost alternative to having new made, I would be concerned over the weight of some of them.
7/16 inch is not such a strange fraction. You're too young!
Of course this would have been the finished hole size in the bush using a 'standard' 7/16 reamer and OD of cam follower would have been ground very slightly smaller to give the desired running clearance.
Happy New Year
I always thought it was the bush that wore not the followers!
"Foreign" cam followers,
I made my own followers when I could not replace my knackered originals. I got rid of the tappet bush and made followers that ran straight in the pushrod tunnels to my own design, to see if an alternative arrangement could work. After 600 miles I took them out to see (see image). I was happy. Nearly 7,000 miles later, ( I have not even adjusted the tappet clearances) they are still there. I am running them till they break. This has shown me that alternative followers can be used. I have since found stock VW beetle type 1 followers fit straight into the pushrod tunnels with the same tolerances as the ones I made, as they are mass produced they will perform better than any I could make. The followers I made are heavier but I have been 70mph in third gear which is a good enough test for me. The other images show how they fit. A bench test of a lightweight engine is required to evaluate findings before it could be used .
oil leaving the cylinder head and collecting in the push rod tubes.
You asked how the oil would drain down past the VW beetle followers if they fill the pushrod tunnels. This is what has to be investigated preferably by bench testing. I would leave the left cylinder with original tappet guides and tappets and fit the VW beetle arrangement in the right cylinder and run the engine and leave the rocker covers off. If oil accumulated in the pushrod tunnels more on the right cylinder then drainage channels could be ground in the cam followers to relieve that build up. I did this on the cam followers I made (see image) copying the ground drainage channels as used in the rocker spindles (see other image). This experimentation is not too "risky" because the problem is too much oil lubricating the followers , any build up of pressure will force oil to pass through the drainage channels in the VW followers (see image).
Good afternoon all,
Absolutely fascinating stuff! I'm most impressed with your engineering expertise and ingenuity - sadly well beyond mine! One question - have your experiments resulted in a quieter Navigator engine? I have never heard a Lightweight running with new / unworn cam followers so don't have an objective view of how much noisier cam followers with worn shafts are!
Graham: To a layman's eye the thicker VW cam followers have a much bigger surface area to their reciprocating shaft which spreads the side loads which presumably wear the originals so quickly. I guess the down side is an increase in reciprocating mass which might promote extra wear on the cam lobes / rest of the valve gear or limit revs?
Barry: Keep us posted on how the Ford solution works out - given the robust nature and long development of the Kent engine and it's racing success in highly tuned states I would hope they would last far better than the originals! With their financial and metallurgy resources if Ford can't make long lasting cam followers then there is little hope for a long lasting solution funded by the club!
John: Interesting to hear about the wear in your guides, like you I had always believed the accepted wisdom was the guides don't wear!
Thought for the day: Is the most cost effective answer using Ford cam followers and the Club funding the manufacture of slightly longer pushrods?
On the subject of cam follower bushes , I have two sets removed from barrels , both of unknown mileage . All 8 are worn bell mouthed at each end . As mentioned above , I was intending manufacturing new bushes with a reduced bore to suit the original followers I had ground to minus 0.010 ins . ( 0.427 ins) . The difficulty would be “broaching “ the oil return/ lubrication channels , but I think I could do this using my lathe .? I assume Norton used cast iron bushes to match the expansion rate of the C/I barrel. Does anyone know if alternative materials have ever been used ? In particular phosphor bronze . The oil drain channels are on the inside of the bush to direct retuning oil on to the cam lobe faces . I read on one of this forums threads , that someone had drilled additional drain holes close to and parallel to the bushes to aid drainage , but have no knowledge if this was an improvement, or resulted in a drop in lube reaching the cam lobe faces.
For the record Kent follower Measurements are Shaft dia 0.04365 ins . Head dia 0.850 ins , shaft length 1.848 ins.. The original Norton followers measure , Shaft dia 0.4365,ins. Head dia 1.040ins , shaft length 2.288 ins. Width of cam face is 0.510ins . As can be seen the Kent follower head dia, although smaller than the Norton , is considerably wider than the cam face . The shortfall in the follower length is 0.0440 ins hence the need for longer pushrods .
Just had a read through the comments here and would like to comment.
The VW followers, If they are 19mm diameter then they are already 0.002" too small. The bore of the hole for the guide in the cylinder is, according to the W/S manual 0.7505/0.7495". Therefore there could be as much as 2 1/2 thou clearance, far too much. An initial clearance of 0.0005/0.00075" would be a good starting point. I'm assuming the VW guide is exactly 19mm diameter and the holes in the cylinder block required no "cleaning up".
The Ford followers, too short. That seems to be the problem with these engine. I think the proof is that the guides followers seem to wear excessively in a "bell-mouthed" way.
Interesting that the guides can be fitted so they are closer to the cam, some possibility that the all important length can be increased.
Oil drains, what ever solution I choose to sort out worn guides I am going to put the oil drains on the outside of the guide. Then arrange a means of holding oil on top of the guide (a large countersink?) that should improve lubrication. I think that the existing arrangement can clear the oil too quickly from the guide, oil will take the path of least resistance. That is to say the oil will pass through the drains rather than find its way into the bearing surfaces where its needed.
I soaked the ends of a Dommie pushrod in strong caustic soda solution to remove the push rod end. The push rod tip went black, but no other damage or corrosion. It took some hours because the alloy is surrounded by steel. Anyway - no mechanical harm to the end, and it's worked fine ever since
Barry has been really bold and made real progress.
I would just like to repeat my warning that the Ford Kent follower may be a bit small.
The face of the follower takes the contact with the cam, that is obvious.
Only at maximum lift is the contact line across the centre of the follower face. (assuming the cam follower centre line intersects the camshaft axis of rotation)
At the beginning and end of lift the contact line is well off the centreline of the tappet. The contact line progresses towards the centre at maximum lift and passes through to the far side as the cam continues rotating.
Thus the wipe area of the cam is a rectangle, as wide as the cam face, and as long as this wiping effect.
I can see in some worn tappets in my hands that the 'wear' area appears to be about 23mm diameter. It is circular, rather than rectangular, because the tappet rotates.
The tappet rotates because current thinking in the '50's was that it is better to slightly offset the cam to the tappet, encouraging tappet rotation and more even wear of the follower.
Provided the Kent cam follower, at 0.850 ins, is wide enough to cover the cam ( 0.510 wide) at maximum lift, whatever the axial tolerance of the camshaft location, there should be a workable solution.
If the rectangular wipe area goes outside the face of the smaller Kent cam follower, (which I think it will if my observation of 23mm above is correct) the contact pressure between cam and follower will be increased at the initial lift and fall of the cam. A real risk the lubrication will fail.
Something to think about.
Wear and Why ??
The lightweight cam follower (A39 20875 called Tappet assembly) and follower guide (A4020751 called Tappet bush in cylinder) show wear when inspected ,with the follower stem going oval and the bush guide belling top and bottom. This indicates to me that the follower is experiencing side ways forces as it rises and falls following the cam lobe. The running cam diameter of the camshaft is approx 25.65mm and the lift on the cam lobe approx 6.6mm. This means the cam lobe is walloping the cam at a point wider than the shaft diameter (11.1mm 7/16"?) and makes the stem scrape up the guide bush when rising and falling. Perhaps quietening ramps on the lobes are supposed to deal with this but wear shows it is not enough. If the stem diameter can be greater than the widest point that the cam lobe can wallop the cam face (in a straight line from that point to the rocker arm) the side ways forces will disappear and the cam will lift straight up and down.
The observation that cam wear is 23mm is partly because when the stem and guide wear the cam face rocks back and forward in a typical ducka-ducka sound (some will have heard) increasing the diameter of the wear pattern on the follower face ,the more worn the assembly is the larger diameter.
Making a follower that runs directly in the pushrod tubes was my solution to the wear patterns of the lightweight assembly I suspected. The sketches attached show the arrangements.
I believe the Lightweight tappet is hollow as shown in your drawing sk1cam.jpg. I congratulate you for the accuracy of your drawings. Did you section a or dismantle a tappet to make the drawing? And would you be prepared to lend it to me in the quest to get more tappets made?
I have to be careful on this the NOC forum now I have a role on the NOC to get parts commissioned. I cannot sanction non-standard modifications, no matter how good they appear, as it may be interpreted that the NOC sanctioned their use and is partly responsible for the damage/injuries caused when the follower head (for instance) fell off, causing an engine seizure, when overtaking a HGV at 70mph on a single carriageway etc.
By all means explore alternatives and report back please.
For now, it's more (A39 20875 called Tappet assembly) and follower guide (A4020751 called Tappet bush in cylinder) for me.
I hope you understand and I think your alternatives look great. SK2cam.jpg with a longer pushrod and some way of draining oil from the rocker gear looks the best from a point of view of reducing side loads on the tappet. Have you tried it?
I can send you the dismantled tappet no problem. Text me an address to send it to on 07724121414. The tappet is knackered so no need to send it back.
I have had my cam followers (SK2.) in my bike for 3 years. Many nervous trials in the early days waiting for seizure or failure. Tentatively exploring 5mile, 10mile, 50mile, 100mile tests. Confident now having done a few 200mile runs on motorways and fast dual carriageways cruising 60 to 65mph (now more of a test for me than the bike). I only undertook this experiment because I could not get replacement tappet assembly or tappet bushes. My thoughts at the time were , if I make my own what makes sense based on the wear I observed on the worn tappets I removed. I only went ahead with this dubious exercise in the knowledge I have a spare engine to fall back on if the worst happened . Other Lightweight owners may not have that option to experiment. Just letting the forum know that alternatives are possible.
I've just removed the 3 remaining guides from a spare cylinder. I've measured the "holes", a very consistent 0.0003" over 0.750, impressed with that!
I think that the VW followers are a non-starter, too much clearance, half worn when new, see my previous post.
I do like Grahams long followers (SK2), how does the oil drain past? I think there is enough metal in the cylinder to bore the holes a little bigger, along with a reduction in diameter of the long follower to fit a bush with external slots (3?) to provide adequate draining.
I think the problem is that the followers are too short so the Ford parts are also a non-starter. I've been looking at B and C range triumph followers (non-rotating). They are longer but smaller in diameter, they do not have problems with excess wear. The Norton followers are supposed to rotate which they do to a certain degree, enough to cause the guides to bell mouth evenly all around the diameter, likewise the wear on the follower, seems to be fairly even spread around the diameter.
I'm going to investigate a couple of "foreign" followers, both much longer, the key to resisting the side loads is, principally length, the diameter has less to do with it.
It has been suggested the hard Chrome plate is used on the follower face, I thought AMC gave up on that when it stared to flake off? Needs to be a Stellite material like Triumph used.
There a lot of stuff on here to wade through.................almost too much, have lost the will.
So, back to the beginning...
The original followers were made by a process called 'end upset', where one end of a rod is heated to cherry red & thumped down onto a flat surface, thus creating the flat mushroom head that we know. This is a cheap (induction coil?) and quick method of production, without any waste and possessing a good grain flow.
I already could not buy them new in 1978 - they were in short supply even then, and so I commisioned the first batch of 100 back in the 1980's or 90's. We could not do end upset, so each one was machined down from solid.
The originals were hollow in the centre (to keep weight down) with pressed in end caps. The down side of this design was that the guides are extremely short, and with the cams lifting them off-centre (to ensure they rotated) the stems ended up wearing into a barrel shape. The tappity noise you hear is usually the cam followers rocking to and fro in their guides.
In the batch I had made, I experimented by making them in one piece without an end cap, with the idea of running them in longer guides - for which there is room. The penalty was that they were heavier - & we never pursued the idea of longer guides as Russell Motors (I believe) provided us with a big batch of new original ones. I have yet to dismantle an engine containing these followers I had made, so have no idea how they stood up to being used. If anyone has seen one, I would really love to know.
These followers were labour intensive to make, and to correct an assumption made above - the stems are case hardened, while the foot is hard chromed and ground flat to a mirror finish. They weren't cheap to make - but despite that we sold all we made, and I believe more were made since - more faithful to the original design.
The NOC have the factory drawings.
I found that Renault engines used a very similar design follower at the time, but dismissed it as the flat head was only half the size - that was the closest I came to an alternative.
Having now got this off my chest - I will attempt to read the previous contributions.
Having waded through the above, I am pleased to see so many innovative ideas.
Immediately - I have to sound a warning. In the early days of experimenting, I too was told the faces should be Stellite, so I went for it. It just destroyed my cam.
So, for whatever reason, stick with the Hard Chrome on the face. It works. The factory spec was 5thou min deposit & ground to a mirror finish.
The stems were 'carburised' (hardened) to a depth of 0.025"/0.030" and centreless ground to final size 0.4360"/0.4365" dia. VPN 750/820 after hardening.
I like the idea of the follower using the whole hole (as it were) - but I worry about the weight of it & draining the oil down from the head fast enough (esp on engines after 106838 & Electra that had the double speed pump!).
The Ford follower looks nice - but is a tad short at 1.85" (against 2.29" of the original) - so even more susceptible to wear on the shaft - the Renault ones I found years ago were the right length - but had a smaller diameter head.
The talk about the follower being lifted off centre is a legacy of the original design. The Jubilee was initially designed to have a one-piece head and barrel in rotary aero engine style. That is why the valves sit rather more upright than normal (so they could be inserted up through the cylinder) and the cam follower was going to be one piece all the way up to the valve - hence the very high cams. Late in the development stage it was decided to have a detachable cylinder head (as we liked de-coking our bikes on a weekend) and so the short followers & pushrods were created. The cam still lifts the follower with an offset to ensure that the (original long) follower rotated. It does do that, but sadly it also places an extra axial loading on the stem - & thus it wears barrel shaped.
A complete 'fix' would involve longer guides and placing the cam on the centre line of the follower - but then would we run into trouble with uneven wear?
And yes - the guides are made from cast iron - for two reasons 1) as has been hinted at above, so that they expand at the same rate as the barrels, and 2) cast iron is self-lubricating.
I have kept all my worn followers (have you?) - I may have 40 or more of them - hoping that a remanufacturing process may be found one day - that would be my preferred option.
Thank you for all the fantastic ideas and research being done out their to find a solution to this difficult and complex problem, hugely encouraging!
If we are tomake our case for the Club to fund a solution could I encourage everyone to find the time to support Peter Holland in his NOC work commissioning the manufacture of new parts / or renovating old parts. He can only show that there is a market out there if members add their names and requirement for spare to the thread on the 'Commissioning new Parts' forum found at the bottom of the Forum page.
You will find it via this link: https://www.nortonownersclub.org/node/11794
I for one like Andy Sochanick's idea of a renovation service for old followers.....I'm not an engineer but I wonder if modern metallargy or hardening processess could provide a long term solution despite all the design limitations of the followers and guides?
Eternally optimistic Nick!
For what it’s worth , I weighed an original follower ( albeit a worn one ) and an unused Kent one and established the Kent was 3.5 grams heavier.
I have now manufactured a set of 4 cam follower bushes and successfully broached the oil return key ways ,all done on my lathe . I used spun cast spheroidal graphite (Meehanite ) cast iron which has good self lubrication properties. I have made them slightly longer than standard by 3 mm as there is room when assembled. These are bored to 0.4285 ins to accept the set of original cam followers which I had ground to 0.427 ins to bring them back to parallel. The top end of the bushes has a larger countersink which I think/ hope , will act as a reservoir, aiding lubrication. I now have choice of original new bushes and Ford Kent followers , or my reground original followers and the bushes I have made . I will use both as I am building a spare engine , but am still undecided as to which goes where . Pictures show the original bush on the right and my version on the left . Hopefully as there appears to be growing interest , the club may be able to have a quantity manufactured .?