Valve guides

What were the original guides made from?

I would make them from phosph/bronze if it were mine..

triumph used both but cast iron last longer and is fine for road use

I would use phos/bronze any time they are likely to fit better and last longer. I worked for Dresda Autos and they always replaced guides with phos/bronze.

David

As an alternative to phos bronze look at "Colisbro" a berrilium copper substitute.

As the original poster has the cast iron it will last a long time, not many old bikes do big miles these days.

If the head is alloy then the interference fit of a cast iron guide may be a tiny bit more critical than phosphor bronze as the bronze is a better match for the expansion rate of aluminium. Norman Hyde recommended assembling the guides with the head and guide cold, the tool was a simple screw puller that lets you feel how tight the guide is in the head as it is drawn in. If it goes in too easily then consider an oversize guide. An old engine may well have had a number of guide fittings and the heads do wear with each fitting. Cold extraction will give an idea about how tight the old guide was in the head and measuring the guide will give a target to aim for or if it was not too tight a fit in the head it may be worth adjusting the size of the new one to get a firmer fit.

Mike

Cast iron works fine in ally heads. Harley have been doing it for years. They regard it as having better wear factor than bronze. But the go fast guys like to put in bronze guides because of supposedly less friction. I've used both, in both Harleys and Brit bikes, and can't say there is any difference that you notice between them in real life useage.

I know this might well go against the grain when we have workshops of our own, but how about seeking a local engine re-builder to see if they have the relevant internal thread knurling tool.

My preferred re-builder for Rover V8s has a gizmo that he bought in America. The idea is, that rather than replacing the guide, one takes a worn guide and knurls a fine thread inside it.

This has several advantages, or so he tells me, less friction on the stem, no need to replace the guide and risk a loose guide in the head, or wearing the head. Also the knurling traps oil by capillary action, both lubricating the sliding surfaces, and also preventing oil running down the exhaust valve stem, it's held in place by capillary action, eliminating the blue smoke on startup.

It's often thought of as a bodge in the UK, and in some cases this might be true, but on competition engines, some folks stateside will even ream out a new guide to make more clearance, so they can then knurl the inside.

Bill

I made and fitted a couple of new guides to my Humber 1929 motorcycle yesterday, the old guides were OK but I have fitted modern valves which are a lot more durable than the original which are prone to drop a head.

Cast iron was the material used originally and is best used in exposed valve gear as it wears less readily when exposed to road grime compared with phosphor bronze.

Cast iron will be fine for the triumph valve guides, as advised, be very careful over the fit. Plenty of advice suggesting using Ph. bronze for valve guides. It is not a suitable material for valve guides, it will eventually suffer from the effects of heat, particularly around the exhaust valve. I think Ph. bronze is confused with Aluminium bronze, both difficult to machine, Al. bronze being far more suitable than Ph, bronze, as is cast iron. Columbia metals do "freecutting" versions of various bronzes, as suggested "Colsibro" (Al. Bronze) being very suited to valve guide usuage.

There is only one bearing in an IC engine that would benefit from being made Ph. bronze, the small end bush, highly loaded, marginal lubrication and runs hot. The Gudgeon (wrist, piston) pin will be very hard, its this combination of material/hardness that works well.

Cold extraction/insertion of bearings in Aluminium housings should be avoided, you might get away with it but what tends to happen is metal will be scraped out of the hole, destroying the size/geometry of the hole, then that hole will need repair.

Peak4, never heard of that process, its not a lining process is it? On larger engines the guides are bored, in situ to take a liner. This process was developed to speed up the repair time, time is money! if the guide is "knurled" then surely oil will leak down the guide, do you have a link to the guy who does this?

.

John,

I had never heard of it either ... but I presume this is the process [even if not the specific device]

**LINK**

https://www.hastingsmfg.com/ServiceTips/valve_guide_knurling.htm

MichaelG.

Michael G, thanks for the link, interesting. Looks like a "quick fix", the bearing surface must be substantially reduced with a related reduction in life. If the knurled surface is anything like that we might put on, say, a thumbscrew then the oil will have a direct route down the guide, something engine designers and manufacturers go to some length to avoid. This will play havoc with emissions.

I could be wrong, but as I said a quick cheap fix.

John

Having a look at Michael's link, the knurls look they are parallel, annular grooves, not diamond pattern, thus providing low friction, oil retaining, labyrinth type seals. All desirable properties in a valve guide.

( did I use enough commas in that first sentence?)

Rod

Don't most car valve guides have seals to prevent oil going down the guide? It is a mod on the Trident to fit inlet guide oil seals to improve the poor oil consumption of the non sealed engine. A razor sharp chamfer is another ploy to stop oil sitting where it can be drawn down the guide. As the valve gear on Meriden Triumphs puts a significant side thrust on the valve stem they tend to wear a bit oval quite quickly.

Mike

That's pretty much the process as described to me by "Pete the borer".

He bought the tool in the US many years ago, but I've no idea what make it is, and I've more or less lost contact with him as I've not needed any engine work done for some time.

I believe it's a fine knurled thread, not a diamond pattern, or annular grooves, so I guess analogous to a rolled thread on a cylinder head bolt, rather than a cut thread.

It doesn't provide an easy path for oil to run down the guides, rather the oil is retained there by capillary action.

I'm not sure how many miles are now on my 3.5 V8 heads since he did the work, but probably greater than 100k, and no blue smoke puffs on startup.

Bill

From across the pond valve guide knurling was done a while back, don't know if it is still done, but was told the job would not last as long. How long it would last is Your best guess, same as piston knurling.

the tool bruises and swell the metal guides.......

think of a dog rough tap, after that u just run a reamer or broach down the hole......re-cut the seat and ur away....

the guides def. don't last as long, so u'll only get from an cast iron guide a 100,000 miles instead, 1/2 million from bronze.....

the yanks were using this in the early 70"s when I was there.......

cost is the main reason for using this tool cos most just don't want to pay......

anyone worth their salt now uses "Serdi" valve equipment, French made and the best, all the fast boy's use em......now I think a couple of m/cycle engine rebuilders now use em.....

not sure but heard they are over £20,000.......but they are very special........

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