K: Tools Removing the inlet valve guide retaining rings.... the hard way

[Jim Bush]

Two weeks it has taken to remove two inlet guide retaining rings, pretty sad.
4 broken tools including Robert Watson’s special bespoke unit.
Thankfully I was able to reclaim Robert’s by milling new tangs (big apology Robert).

The KTB gives a detailed drawing of the tool (Fig 11, page 119) – and instructions are to use high tensile steel, ie an old car half shaft. I didn’t have an old car half shaft on hand, being a motorcycle shop, but I did find half of a Norton gearbox main shaft.

I was able to machine the extact tool, with milled tangs and internal thread on both ends.. Trail fit, ok, heated the head, installed the tool, tightened centre bolt, ready to undo… and snap, both tangs broke off – maybe not high tensile after all.

Decided another approach would be required, I machined a piece of ¾” HRS with 3/8” BSF thread on inside and 2 flats for a 5/8” wrench on the other end.
I laid out the dimensions and drilled 2 x 1/8” holes and hammered in some cut off HSS drill bits and shaped them square-ish with the Dremel.

Same, process, same result, bent and sheared off.

Since the broken pieces were still in the tool, I had to lay it out again and drill 2 more 1/8” holes.

I found some 1/8” carbide bits that were cut off, shaped and installed …. they worked! Eureka!

What a process.

Now I still have to shorten the top of guide by top cutting and machine the brass retainer ring for the oil seal.

24 hours sounds about right for this operation? … no wonder these engines cost so much to rebuild.

 

[timetraveller]

I designed a part which will hold the lower valve guides in even if the thread had been ruined. They are available from the Spares Company and will avoid all this in the future.

 

[bmetcalf]

I never finished it, much less tested it, but in the '80's I started on a tool for this using an old socket wrench. I had a piece of 3/8" square stock with a tapped hole in the end for an allen screw to pull the tangs against the ring. The socket would have had tangs sculpted in it with my trusty dremel cutoff wheel and would have been keep in place on the square stock with a weld. I thought that the '70's vintage socket steel would be tough enough for normal duty, but your case seems very uncooperative.

 

[Peter Holmes]

I designed a part which will hold the lower valve guides in even if the thread had been ruined. They are available from the Spares Company and will avoid all this in the future.

Norman, this is not in anyway a criticism, just an inquisitive enquiry, hopefully I will never need your device, but if I ever do, how does it hold the valve guide in interference fit ( shrunk in with heat) in the head, I really struggle to understand that if the valve guide loses its fit and it is not clamped in place with the threaded lock ring, what stops it fretting away the head with The small movement created, as I say, just interested, that’s all.

 

[timetraveller]

No problem Peter,I am happy to try to explain what it can and cannot do. The device can serve at least two purposes. First I should make it clear that it is not intended to hold a loose guide into a worn hole. For that purpose an oversized lower guide is required but that is simple enough that any reasonably competent machinist could make one. Instead, and assuming that either the original hole and guide are a good fit or an oversized guide had been made and fitted, then my gadget can hold the guide in place either with or without a seal. It does not require the thread to be still usable and from my experience if the guide has been fretting up and down it is likely that the thread is also u/s. It is made long enough, and with its lower end designed in such a way that it can either just hold the guide down or do that and support the type of seals provided by the Spares Company. If the thread is still in good condition then the bottom of my gadget can be machined off and its length tuned to trap the screwed lock ring so that it cannot start to move up and down. That way it will hopefully prevent future problems with fretting of the guide and lock ring. I think that I posted some photographs when the batch had been made but I can always produce some more if required.
I've just had a look on the Club Shop web site and cannot see these items. Either they have sold out or they are not happy with them. If it is the latter then I need to know what the problem is if there is one. If the former then I can get more made as I paid for the CNC program for the first batch, They are made of 7075 so really tough.

 

[The VOC Spares Company Limited]

No problem Peter,I am happy to try to explain what it can and cannot do. The device can serve at least two purposes. First I should make it clear that it is not intended to hold a loose guide into a worn hole. For that purpose an oversized lower guide is required but that is simple enough that any reasonably competent machinist could make one. Instead, and assuming that either the original hole and guide are a good fit or an oversized guide had been made and fitted, then my gadget can hold the guide in place either with or without a seal. It does not require the thread to be still usable and from my experience if the guide has been fretting up and down it is likely that the thread is also u/s. It is made long enough, and with its lower end designed in such a way that it can either just hold the guide down or do that and support the type of seals provided by the Spares Company. If the thread is still in good condition then the bottom of my gadget can be machined off and its length tuned to trap the screwed lock ring so that it cannot start to move up and down. That way it will hopefully prevent future problems with fretting of the guide and lock ring. I think that I posted some photographs when the batch had been made but I can always produce some more if required.
I've just had a look on the Club Shop web site and cannot see these items. Either they have sold out or they are not happy with them. If it is the latter then I need to know what the problem is if there is one. If the former then I can get more made as I paid for the CNC program for the first batch, They are made of 7075 so really tough.

No problems with them Norman, All customers happy.
They are on our home web-shop page, Featured/New products, part number ET122-Walker widget.
Bob

 

[timetraveller]

Thank Bob

 

[ClassicBiker]

Norman,
When you sent me the drawing for the widget, before they were carried by the VOCS, so I could repair my Shadow's front head, I thought what a brilliant idea. My only regret is only making the one. Three of the four lock ring threads were still good. In retrospect, I should have made modified ones to prevent the three remaining lock rings from backing out, even though I thoroughly cleaned all the threads and red Loctited them. If I ever have to get into the heads again you can bet I'll be making and fitting three more.
When I get around to rebuilding my Comet, you can be assured that I'll be making a pair and fitting them. Regardless of the condition of the lock ring threads.
When thinking about it, I can't understand why P.E.I. didn't use something like this in the first place. It is far a simpler solution to preventing the lower valve guide from creeping out than what he designed.

 

[timetraveller]

Thank you for your kind comments and happy to be of service. It seems to me that it is this kind of thing, i.e. helping each other, that this club should be about.

 

[vibrac]

The idea of a holding screw to firmly hold the tangs in place is a policy I have often used I use the technique for instance on the gearbox selector plate pin G34 where my tanged tool uses the handy central thread