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Navigator cam followers and guides

Submitted by nicholas_clarke on Fri, 22/03/2019
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Light Twins

Dear all, although my Navigator is running well I am looking at how I can improve the engine both in the short term and planning ahead for the inevitable engine rebuild in the next few years.   I have read much technical wisdom over the years about how the cam followers wear into a barrel shape because of the side loads on them which after relatively low mileage adds to what is already a notoriously mechanically noisy engine.   Various comments on historical threads suggest the cam follower guides don't wear - is that true?   Looking at the NOC shop they sell new cam followers and guides but they are certainly not cheap!   My questions are:   Has anyone replaced just the cam followers and if so was there a noticeable difference or is that a false economy and it is always worth replacing the guides too?    Has anyone replaced the guides, if so how difficult are they to drift out and replace and having replaced the cam followers was the engine noticeably quieter?    Having replaced them is there any proven modification that cuts down cam follower wear or is it just a reality of lightweight ownership?   Finally, how quickly do new cam followers last in normal use before they wear and become noisy again?    Cheers  Nick          

Submitted by dennis_thompson on Sat, 23/03/2019

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Can't comment on the cam followers other than to say that on my worn Jubilee engine the cam followers are still a snug fit in their guides and no sign of wear on the contact surface.

The valve guides however were very worn and were difficult to drift out and replace - lots of heating in the oven for 30 minutes and hammering at the guides with pauses to heat again when the head (cooled) rapidly and the guides would not budge. I had to heat the head two or three times per guide. Getting new guides back in was just as difficult and I ruined one guide by not having the correct diameter shouldered drift. You may need to get a drift made or borrow one as the those sold commonly for BSA and Triumph are the wrong size. It would be better in my opinion to get the guides pressed in if that is possible. I put the new guides in the freezer overnight before fitting them and heated the head as before. You must not damage the lip of the guide.

Others may have a better technique.

Dennis

Submitted by nicholas_clarke on Sat, 23/03/2019

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Thanks Dennis, that is very interesting about your cam followers.    It also reminded me of previous battles to change Jubilee valve guides - you are right about having the guides pressed out and in although I have no idea how that could be done given the angle they are at!    perhaps others can advise?

Nick

Submitted by nicholas_clarke on Sat, 23/03/2019

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You are probably right Dan, it just offends my mechanical sympathy - perhaps Norton intended it is a natural rev limiter!   In fairness apart from a weeping timing side oil seal which I will replace as soon as I can find the time the Navigator was running really well today and looking much better for the new front rim and handling better thanks to new tyres and rear wheel bearings.   To be honest I will probably leave well alone until it needs a top end overhaul, it would just be useful to know if new cam followers and guides are worth the expense and challenges fitting them!   I hope your Jubilee and Navigator are in fine fettle for the spring...….when it finally arrives!   Nick       

Submitted by dan_field on Sun, 24/03/2019

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I’ve been running the jubilee all winter, the Nav is still in bits because my M50 is not in a good way! 

Dan

Submitted by peter_holland1 on Mon, 01/04/2019

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Nick,

I've noticed that cam followers go barrel shaped. When worn they probably contribute to the noise and will not be holding the cam follower square onto the camshaft.

Easily checked by measuring the cam follower shaft in three places with a micrometer. IMHO when the difference max/min exceeds about 0.1mm you might consider a replacement follower. 

Check very carefully that the stellite flat surface on the bottom of the follower is not worn through in the centre or chipped at the edges. A symptom is cam lobes worn more at the sides than the centre.

If you decide to renew the cam follower bushes/guides these can be drifted out, cold, with a shouldered drift. The slots should be positioned so that they are across the engine. Bushes are not positively located so be sure to note how much protrudes top and bottom before you remove the originals. I agree with others that these bushes don't seem to wear as fast as the follower shafts.

The picture shows four followers taken from a Navigator. Chemical de-rusting highlights the worn stellite surfaces. One OK, and three replacements on their side.

Cheers,

Peter

 

Hi Peter  your picture confirms the typical wear I found on my camfollowers. The rattle between the barrell follower stem and the follower guide is where all the noise comes from. I made my own followers to attempt to get round this. I inspected my followers after 500miles  see 2nd image. I have subsequently gone 3000miles and will only inspect again if there is mechanical failure. It is the only way I will find out if something can be done to deal with the wear that all these lightweights seccumb to  because of their design.

GRAHAM

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Submitted by nicholas_clarke on Mon, 01/04/2019

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Thank you, that is very helpful Peter and confirms everything I had read elsewhere and heard over the years - and your pictures tell a very sorry tale of excessive wear and are a salutary lesson!   I note that the NOC doesn't have Navigator cams in stock so avoiding cam lob wear has to be a priority.   Did you replace your followers and guides and did it result in a significantly quieter engine - and if it did has it stayed that way or do they wear as quickly as others suggest?

Nick 

Hi Nick,

Reading Graham's comments suggests he is the person to tell us all if the new replacement tappets reduce noise. I get the feeling from his comments that indeed the fit of follower to guide bush is the major noise factor.

I have to applaud him for making his own cam followers. 

Those available from NOC were made by the club -way back. The stems are hollow and the hardened socket on the top is pressed in, covering the hole down the stem. Then the outsides are hard chromed and flat faces dealt with likewise. Then finish ground. This is where the cost comes in. The cast iron bushes are easier to make reflected in the cost.

The camshafts are unavailable through NOC or any other outlet, I believe. It makes sense to look after them.

For some reason I can't explain, lightweights seem to get condensation and rust in the camshaft/cam follower areas when laid up for a few years. The rest can be fine but the camshafts seem to get rust pox too easily. This may be why we have no camshafts left.

My own experience is limited to a rather large stash of used lightweight bushes and followers. Some are incredibly worn and some hardly worn and I just pick the least bad. Not the best person to tell you if a new follower and bush will silence the engine.

Regards

Peter

 

Submitted by nicholas_clarke on Tue, 02/04/2019

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Great bit of engineering Graham and thanks for that!   From the look of it you not only made your own cam followers but guides and push rods too - am I right?    What materials and treatment did you use to harden the cam follower working faces?   Has it made a significant difference to the mechanical noise form the engine?  

Nick  

Submitted by ian_hart on Tue, 02/04/2019

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I'd read somewhere, some time ago that Ford 'Kent' OHV cam followers were not overly dissimilar to those of the Norton lightweights.  The general 'top hat' shape is much the same and the shaft diameter is 13.1mm apparently.  However, the finish of the Ford items may be inferior and their weight might be heavier.  I wonder if anyone has appraised them as an option?

Also, I had wondered whether or not the wide slots cut down the flanks of the cam follower bushes might reduce the efficacy of lubricant between them and the followers, even if they're aligned correctly.  My early Navigator barrels have secondary drain holes, roughly 3mm dia. in the shallow wells alongside the cam follower tunnels, which led me to speculate whether or not the grooves were an ill-considered afterthought.  (Those drain holes are absent from Graham Squires' photo 034 of a later block.  I'm away from my garage at the moment. so I can't offer a photo of my own blocks.)

Any thoughts from the mechanical engineers amongst us?

Regards,

Ian.

Hi Tony

Replacing worn cam followers with tried and tested production run followers is the way to go. The followers you have identified in your link (I think!) could be made to work if the stem diameter was larger than the the existing ones in the lightweights. The advantage of this is that the existing worn cam follower guides could be re-used by reaming out to the larger diameter follower stem. It is better than that,if wear continues on the new followers then the next time the problem is attended camfollowers of even larger diameter could be used reaming out the guides to the larger diameter like using oversize pistons after a rebore.The larger the diameter of the followerstems will reduce the rocking action that the originals experience.  The only other problem could be if the follower height was different from the originals requiring the pushrods to be modified., simple measurements between the two could find that out. I have tried to dismantle the lightweight pushrods without success ,does anybody know how the pushrods caps was fitted to the  hollow alluminium shafts?

GRAHAM

Submitted by nicholas_clarke on Fri, 05/04/2019

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Thanks for all the useful feedback and ideas Chaps - Oh to have Graham's skill and tools to make improved followers, guides and push rods!    

One final question still remains - has anyone personal experience of replacing the cam followers and guides and did it reduce engine noise significantly and if so for how long?

.....or is Dan's approach the best solution?

Nick

Submitted by tony_ripley on Sat, 06/04/2019

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The lightweight follower is 11.1mm (actually 0.4360 - 0.4365") and I would like to think that the designers would not 're-invent the wheel' if there was something available off the shelf.

This could be Norton following Ford or the other way round. It does seem a strange size to have randomly come up with the same design.

This one is the 11.1mm one.

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

What I am not sure about is the socket where the push rod sits. The lightweight has a tappet end press fitted in. I cannot see from the pictures of the ford ones if they have the same socket. 

The lightweight one should have a groove roughly 1/4" from the end. The ford one does not appear to have that and the groove is in the pressed in part.

Tony

Submitted by alan_osborn on Sun, 07/04/2019

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11.1mm is in actuality 7/16 please remember we are 'British'

 



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