Author Topic: How do you remove the cam followers and guides?  (Read 597 times)

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Group Leader

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How do you remove the cam followers and guides?
« on: 12 February, 2022, 19:45:13 »
I need to remove the cam followers and guides from the B21 engine.   Most of the later ones appear to have the guides screwed in and, most importantly, they have some flats on by which they may be tightened and loosened.

The B21's guides seem to be sub-terrain and smooth; no holes or flats to get a grip on.     

Any ideas on how they are held in and how they are removed?

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #1 on: 16 February, 2022, 20:20:13 »
When the top end is removed from the engine the cam followers should just pull straight up and out.
The bronze bushes - guides - they run in are pressed into the casing. If they need changing they need to be pulled up out of the casing.
A special puller is needed to do that. I made one from a piece of 1/4 plate which bolts onto the pushrod tube mounting studs with a couple of holes drilled through it which line up central with the axis of the cam followers, clearance size for a 5/16 or 3/8 bolt which can then pass through each hole down through the bush to screw into a shouldered collar which locates in the bottom end of the bush.
Tightening the bolt into the collar will drag the bush up through the casing. A tapered washer under the head of the bolt to match the angle it is tilted at will help it work.
Replacement bushes will need to be made from scratch.

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Re: How do you remove the cam followers and guides?
« Reply #2 on: 16 February, 2022, 21:07:20 »
Many thanks for the reply.     

Do I understand you correctly; the bolt passes through the plate then the hole in the guide  with the nut on the underside i.e. closest to the cam and pulls the guide out as the nut/bolt are tightened against the plate?     

My guides seem to be in 2 parts; 1) a thin wall brass/bronze tube fitted into the bore in the crankcase casting and 2) the guide bush itself * which presumably is a a good fit in the thin wall tube and this has the bore in which the cam follower shaft runs.     

If my understanding of your description is correct, clearly the cam follower has to come out first which means the cam spindles have to be removed.

I have another similar casing that has the thin wall tubes fitted but no guide bushes.   Both cam spindles are intact and don't look like they've ever been removed.

Could the cam followers themselves with suitable thread extensions not take the place of the bolt or would that be sacrilege?

Sorry for possibly being a bit dense here!

Alan

* In-fact my exhaust guide seems to have already been gotten at in a previous life and actually appears to be a steel bush with a thin walled bronze tube inserted.  You can see this in the the second photograph.
« Last Edit: 16 February, 2022, 21:14:14 by Group Leader »

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #3 on: 17 February, 2022, 12:44:37 »
There's no accounting for what may have been done to your engine before in terms of butchery and non-standard parts having been made to fit.
Correct re the principle of how the tool pulls the guide up and out of the casing. I put a tapped hole in the shouldered collar for the bolt to screw into rather than using a nut under it.
Correct the cam followers have to come out first. What is stopping your cam followers simply lifting up and out of the guides? Removing the cam spindles to allow the followers to come out downwards shouldn't be necessary.
The original guides which I removed from my engine were solid bronze. It's possible that your ex guide has been replaced at some time by vandervell type steel-backed bush which has a bronze inner surface.
On no account risk damaging an irreplaceable cam follower by using it in some other way! Not really sure how the cam follower could be used as a puller? It simply slides up and down inside the guide, there should be no possible way it can latch onto the guide to then be used to pull the guide up and out of the casing.

Mike Farmer

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Re: How do you remove the cam followers and guides?
« Reply #4 on: 17 February, 2022, 13:24:52 »
 :) :) :)

I am out of my comfort zone with this---but if you turn the cams, do the cam followers move. If so as stated I think they should just pull out. If not! why not?? Are they jammed in.

As I said I have no knowledge of this particular engine so guessing/.

Mike 8) 8) 8) 8)

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Re: How do you remove the cam followers and guides?
« Reply #5 on: 17 February, 2022, 19:54:02 »
There's no accounting for what may have been done to your engine before in terms of butchery and non-standard parts having been made to fit.

And that is definitely the truth!   Many and various of both acts of butchery and non-standard parts.   You'll see an example of the former in the following photograph where a big chunk of the casting is missing (one of many missing bits of casting).

Correct re the principle of how the tool pulls the guide up and out of the casing. I put a tapped hole in the shouldered collar for the bolt to screw into rather than using a nut under it.

I could possibly drill and tap a hole into the top surface of the guide alongside the cam follower stem? - see next point ....

Correct the cam followers have to come out first. What is stopping your cam followers simply lifting up and out of the guides? Removing the cam spindles to allow the followers to come out downwards shouldn't be necessary.

The cam follower itself has a circular head with a flat surface that bears on the cam. The head is a larger diameter than the stem and therefore can't be pulled through the bore of the guide.  I'm not certain that even if the cam spindles were removed you could get the followers out that way as I think the head will foul on the crankcase casting itself.

On no account risk damaging an irreplaceable cam follower by using it in some other way!

Yes that is an excellent point indeed!   Try as I might I haven't seen anything that looks remotely like my guides on EBay etc.   The followers look to be a similar style to those for B33 (See second photograph borrowed from  EBay) but the guide is completely different; there is no threaded part (I presume as I can't see it!) and there is definitely no hex to unscrew it.     Having said that, I can't tie up what is in my engine with the Parts Book for the year (1939) but then I don't fully understand the parts book anyway on this particular subject!

---but if you turn the cams, do the cam followers move.

Yes the cam followers move just fine, driven by the cams when fitted or a finger when not.   The guides are worn so the followers have some side play (mostly at the top of the stem) but I need to be able to remove and recover the followers as I probbaly will replace the crankcase casting for one that isn't full of cracks, bodged welds, holes where lugs have fallen off and been fixed back on etc etc.

Anyway, thank you very much for your continued interest!   I will get to the bottom of it but probably not very quickly.

Alan
« Last Edit: 17 February, 2022, 19:59:31 by Group Leader »

Mike Farmer

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Re: How do you remove the cam followers and guides?
« Reply #6 on: 18 February, 2022, 11:24:21 »
 :) :) :) :)

Guess my input was of little help but it is very interesting. Certainly looks like a bit of butchery to me. Very best of luck and I shall follow this with serious interest.

Mike 8) 8) 8)

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #7 on: 18 February, 2022, 18:08:16 »
Now I see what you're up against.
The cam followers are non standard. Looks like an insert has been pressed into the original guide bush and the non standard follower runs in the middle of that.
I'm guessing that the only way to remove them is to somehow grip the top end of the follower and pull it up, bringing the insert with it?
It may be more a question of do the followers and the inserts they run in really need changing? If the followers go up and down ok without excessive side to side play then leave well alone?
There's one correct original cam follower on eBay at the moment from dynamo dunn, so you can at least see what it looks like. Item 325015367365

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Re: How do you remove the cam followers and guides?
« Reply #8 on: 18 February, 2022, 19:56:35 »
It may be more a question of do the followers and the inserts they run in really need changing? If the followers go up and down ok without excessive side to side play then leave well alone?

There's a lot of side play with the inlet follower particularly but, more importantly, they really need to be in another (half decent) crankcase casting.

There's one correct original cam follower on eBay at the moment from dynamo dunn, so you can at least see what it looks like. Item 325015367365

I'm slowly getting to grips with this now; I've been scouring the parts book looking for something that looks like what is already there but, of course, it's another red herring!   I have already seen that follower when searching EBay but it looked completely wrong (i.e. completely different to what is in there already) - now I know why!
That would also explain why the tappets were so difficult to set as they are partially located "up the tower" and not nicely in the chamber intended for them.   So I'm guessing that another PO modification was custom length push rods to accommodate the over-length  and bushed cam followers.

Do you know what the significance of the partly helical holes are?   Is it to reduce surface area and thus friction, maybe to impart rotation of the follower to spread the wear?  Any ideas?

Anyway, thanks for you help, now at least I understand what should be there so I now have a couple of options 1) try and restore it back to the original (parts permitting) or 2) contrive a similar replacement system to that that is present using more freely available M20 parts (for example).

Cheers!

Alan

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #9 on: 18 February, 2022, 21:01:53 »
Not sure about the reason for the helical slots in the cam followers. Could be to help lubrication, reduce weight or create rotation as you suggest. As far as I'm aware they were introduced for 1939 B models, the 1937/38 followers are just plain cylinders of the same size.
I reckon they could be used if you find some except the adjuster and bottom ends of the pushrods are different.
If you are looking for replacement crankcases, they would need to be the same year and model as yours, I.e.KB21, the 37-38 B21/22 and also the 1939 KJB21 have 'live' camshafts which turn in bushes rather than running on fixed spindles and no timing gear outrigger plate. In fact the whole of the timing side is different.

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Re: How do you remove the cam followers and guides?
« Reply #10 on: 20 February, 2022, 20:52:59 »
If you are looking for replacement crankcases, they would need to be the same year and model as yours, I.e.KB21, the 37-38 B21/22 and also the 1939 KJB21 have 'live' camshafts which turn in bushes rather than running on fixed spindles and no timing gear outrigger plate. In fact the whole of the timing side is different.

As you've spotted my KB21 has fixed cam spindles and the outrigger plate (that's got to be a better design hasn't it?).      I thought I'd see how tight the cam spindle fit in the casing is.  The answer is not very and a gentle drift with the copper mallet had them out.  The anti-rotation pins remain tight in place.   At least the absence of spindles will give more room for maneuver as I concoct a scheme for extracting the non-standard guides and followers.

If you are looking for replacement crankcases, they would need to be the same year and model as yours

That might be a challenge too far as B21 de-luxes seem particularly thin on the ground and spares more so.      However, I have managed to source a good case from the same base casting which looks to be identical with the exception of the machining around the cylinder mounting that will require some engineering.   I have a plan ......

The immediate task is to work out what to do about the cam followers and guides.

Alan

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #11 on: 23 February, 2022, 21:25:44 »
I'm interested to know what sort of alternative crankcase you have as a replacement?
The other KB engines which have the fixed spindles and outrigger plate are the 350cc engines for 1939. Using them with a 250 top end would mean serious alteration to the crankcase cylinder base joint face, moving the cylinder head studs for starters.

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Re: How do you remove the cam followers and guides?
« Reply #12 on: 01 March, 2022, 14:53:06 »
Indeed.   I don't know what engine the replacement casting I have found is from, it is the correct casting number and the machining on it looks identical to the original with the two exceptions you have mentioned so some "significant" work required to make use of it.   But compared to the replacement B21 casting (that I haven't got ....) at least I'm in with a chance!

I also have a replacement drive side casting with the correct casting number but that is from a B23 which also has similar problems with the addition that, because it was a side valve engine, the tapping for the rocker oil return pipe has not been machined although that's a simple problem to solve in comparison.      However, at the moment, I'm trying to re-use the original drive side casting as it's major flaws are the "not very pretty" replacement lugs.   I can probably live with "not very pretty" lugs as long as they are mechanically OK and to do so would retain the engines identity (just shows you how silly the whole concept of "original engine based on the specific bit the number happened to be stamped on" is!

Alan

Rupert

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Re: How do you remove the cam followers and guides?
« Reply #13 on: 02 March, 2022, 19:29:10 »
Sounds like "good luck" is probably the right thing to say in reply!
Based on my limited knowledge a couple of things come to mind which may or may not be relevant -
The drive side crankcase half: agreed re the rockerbox drain boss needing to be drilled and tapped if you are using a case from a Side valve engine, B23 etc. The other thing is the breather. On the 1939 K engines this is mounted on the drive side case near the cylinder base, on earlier engines the breather is through the hollow spindle of the idler gear.
If you use a '37-38 drive side half with a 39 timing side half there will be no breathing.
The timing side half - inside the tappet adjusting compartment I believe OHV or SV is cast into the Ali. I think this is to tell at a glance which is which because the SV casing has vertical cam followers rather than angled? More than happy to be corrected on that.


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Re: How do you remove the cam followers and guides?
« Reply #14 on: 05 March, 2022, 13:25:02 »
Here's a comparison of the two timing side castings with the potential replacement on the left and the original on the right.   Both have the same (basic) casting number and are marked OHV.     The main appealing features of the potential replacement are:

     1) The casting is intact, has good lugs and as far as I can see so far no cracks
     2) The bores of the cam followers are not parallel and the follower guides are as intended (thin-wall bronze(?) tubes for full diameter followers)
     3) Good, flat, non-scratched oil pump mating face

The main drawbacks of the replacement are as previously mentioned, the throat is slightly over size and the the head bolt holes are in the wrong positions.

One other discrepancy I have spotted is the timing wheel shafts each have two (bi-directional) helical oil grooves where as the originals have only one (unidirectional) helical oil groove.      Am I correct in thinking the bi-directional grooves would provide better oil distribution along the length of the shaft whereas a single groove will tend to force the oil to one end?   Is this likely to be a problem or an improvement?

The main drawbacks with the original casting are:

    1) Possibly holed case, re-instated with  very poor replacement lugs.   
    2) Numerous cracks between, for example, the main bearing oil way and the side of the casting
    3) Very poor oil pump mating face (would need re-machining flat and possible need for a spacer plate to replace the missing material)
    4) The register to prevent the main bearing rotating is missing and hence may well be the primary cause of the lack of oil/multiple seizures
    5) Great chunks of the casting missing (for example see around the inlet cam follower)
    6) Worn, non-standard cam follower guides and followers still stuck in casting - maybe the act of "forcing them in" caused a lump of the casting to break off?

Anyway, the replacement generally looks to be a lot better bet (at least to me at this point) providing the throat diameter can be reduced and, most importantly, the head bolt holes can be re-located in a manner that will be adequately strong enough to withstand the loads created in this most critical area.    Time will tell ...

Alan