Engine Valve caps

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Brian_Walker
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Engine Valve caps

Postby Brian_Walker » Fri Jan 01, 2021 9:34 am

I have an early 1952 VCH that does not have valve caps on top of the valve stems, I can't remember ever seeing them. Are they really required ? I don't remember seeing any marks on the tops of the valves when I rebuilt the engine. Finally worked out that my engine top end oiling is done from the pump outlet on the timing case not from the return line to the oil tank. (this was reported by Waller as an exception to general practice of other engines)
Strange how there always seems to be exception to the general scheme of things for competition models.
Hope someone can offer advice on the valve caps as I do have access to some if needed.
Cheers,
Brian
1951-52 VCH under restoration

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Bob.Murphy
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Re: Engine Valve caps

Postby Bob.Murphy » Fri Jan 01, 2021 10:42 am

My '58 VH certainly has them and the old ones I removed recently were well 'mashed' - such that it was impossible to use a feeler gauge to check the clearance. New ones sorted that . . but for how long ??

I would hope the valve stems are harder than the caps, but seeing what happens to caps I would rather replace a sacrificial cap than risk damaging the valve stem.

Maybe Ariel didn't expect a competition motor to be run for long periods and therefore left them off to reduce the weight and therefore the risk of valve bounce when being used hard ??

If you intend to tour on the VCH I would fit them as a precaution.

Bob.
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH

john.whiting
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Re: Engine Valve caps

Postby john.whiting » Fri Jan 01, 2021 11:12 am

Whether your engine needs valve caps depends entirely on the valves......purpose made high quality valves will have hardened stem ends ,and need no caps...........on the other hand if your engine has valves made from el cheapo parts store blanks with soft stems,the caps will be required to prevent valve ends deforming ,mushrooming ,as its called........They are not advisable if not needed ,as the possibilty of a cap breaking and ending up jamming a spring,or going down into the camgear is best eliminated.

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Brian_Walker
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Re: Engine Valve caps

Postby Brian_Walker » Fri Jan 01, 2021 11:08 pm

Thanks guys, I will run a file across the top of the valve stems and make sure they are hardened before I fit caps, as John suggested don't want one to visit the timing chest at 8000 rpm.
Brian
1951-52 VCH under restoration

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Re: Engine Valve caps

Postby nevhunter » Fri Jan 01, 2021 11:54 pm

IF the question is asked I would say it HAD them originally. There's nothing very special INSIDE a VCH engine. The caps ARE a LIABILITY. From a practical point of view I'd be rid of them and add the thickness to the valve stem length to keep the geometry correct by adding stellite weld or similar. There's 2 types of stellite. One is better for impact. I'd use that one. Stellite is a trade name. Nev

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Brian_Walker
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Re: Engine Valve caps

Postby Brian_Walker » Sat Jan 02, 2021 1:29 am

Thanks Nev, my engine was running in a speedway bike when I got it so not a factory build I suspect the valve tops were stellite caped and ground but will have to check. I have already had to adjust pushrod lengths to keep the rocker arm horizontal and the tappet adjustment screws in the middle of their adjustment range after I changed cylinder base spacer width, I don't want to have to go through that again.
Brian
1951-52 VCH under restoration

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paul.jameson
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Re: Engine Valve caps

Postby paul.jameson » Sat Jan 02, 2021 9:59 pm

Valve caps are not something I worry about. If I have a suitable set, I will fit them but if I haven't, then I do without. I have seen the mushrooming effect of not using the caps - but that was around 50 years ago on a head taken out of service some time earlier. On my own machines I have had no problems resulting from not using them.
Paul Jameson
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.


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