seizing valves

[Pharisee]

I recently fitted new valves and guides to the aluminium head on my '54 G3. The valve guides were supplied by AMC Classic Spares and the valves came from AMOC Spares. The valves were an easy fit in the guides... I actually thought that they were just a touch on the loose side. When I tried to re-cut the valve seats, the 3/8" diameter pilot for the seat cutter was a tight push fit in the guide... The ground pilot mic'd up at exactly 0.3750" so the valve stems were certainly under 3/8" but I didn't measure them so I can't say by exactly how much.

[George Kaplan]

Hello, forgive me but I am not 100% familiar with these engines but I do have some comments regarding sticking valves.

Are the guides made from bronze or cast iron?

If they are made from cast iron then you must ensure that new valves have the appropriate surface treatment. Most valves these days are made from 214N which is a stainless steel. Bare stainless steel in cast iron guides causes galling and stuck valves. I know this because i have had this happen after a rebuild and only got 8 miles down the road. The valve stems need to be treated, there are various options but the most common is nitriding.

When you buy valves to go in cast iron guides you need to enquire about what material they are made from and if they have been surface treated. If the vendor doesn't know then go elsewhere.

Look on G&S Valves website (they are the only UK manufacturer of valves left and are probably the source of valves from most of the good quality spares suppliers), they have lots of information on there. Also you can buy valves direct from them and at least you will know exactly what you are getting.

Obviously if your guides are bronze then your issue will lie elsewhere.

John

[SPRIDDLER]

Hello, forgive me but I am not 100% familiar with these engines but I do have some comments regarding sticking valves.

All contributions are most welcome George. I'm beginning to lose sight of the wood for the trees

You make a good point. The Club Spares Service guides and valves are cast iron and probably many hundreds have been fitted satisfactorily. However, Chris did say that: "The new valves I put in are the same as the AMOC parts site...." and not that he actually bought them from AMOC parts service, so maybe we should consider that they may not have supplied them or that there may have been a manufacturing or supplier error............
Perhaps Chris will clarify who supplied them............?

[Chris Berry]

Thanks guys
Just to clarify, yes I have purchased the parts from the AMOC site. I have a feeling that the problem is just as simple as insufficient clearance. I am due to get the head back from the engineer in the next day or so. The points that everyone has made to date are very useful and highlights the many complex issues that may arise when dealing with guides and valves. I am considering running a little oil in the fuel for a while until everything settles in but am not sure what benefit this would serve as the guides (especially exhaust) would most probably not receive any lube through this.

Hello, forgive me but I am not 100% familiar with these engines but I do have some comments regarding sticking valves.

All contributions are most welcome George. I'm beginning to lose sight of the wood for the trees

You make a good point. The Club Spares Service guides and valves are cast iron and probably many hundreds have been fitted satisfactorily. However, Chris did say that: "The new valves I put in are the same as the AMOC parts site...." and not that he actually bought them from AMOC parts service, so maybe we should consider that they may not have supplied them or that there may have been a manufacturing or supplier error............
Perhaps Chris will clarify who supplied them............?

[SPRIDDLER]

Just to clarify, yes I have purchased the parts from the AMOC site. I have a feeling that the problem is just as simple as insufficient clearance.

I've never had to ream guides so once it's sorted it would be worth alerting the AMOC Spares folk (and if poss pass on the engineer's figure of how much he's had to ream the guides and the final clearance) to check whether current stock of guides (and valve stems?) is not to spec'n.