New Cam Followers / Tappets

Hi Nick,

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 -

https://www.nortonownersclub.org/node/11368

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.

Regards

Tony

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:-

https://www.burtonpower.com/camshaft-follower-681f-x-flow-pre-x-flow-type-fp210.html

Would fit?

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.

Regards

Tony

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.

I always thought it was the bush that wore not the followers! 

Dan

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.

Peter

Hi Graham,

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?

Regards

Peter

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.

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 .?