Non return valve between oil pump and big end feed jet.

Michael, thanks forcopying the oil feed jet and relief valve parts from the manual. However these aren't whatI seek and I think are all apparent in the photo of my timing cover that I attached. The non-return valvearrowed in red does not seem to be listed, hence my query. Your input appreciated anyway.

Barry, you are probably right in that this non-return valve is missing in many timing covers. I have another 19S and an ES2 in which it is firmly pressed into the oil pump orifice. However on a previous M50 I don't recall one, likewise a spare autojumble cover that I have is missing it. No sign either in my WD or pre-war 16Hs. In the present can of worms that I am working on it's just floating around in the hole ready to fall out when inverted.

I can find no mention of it in the Haycraft, Franks or Garratt manuals, just the briefest mention of it being there in the NOC Singles Engine Video.

Just what its function is, or the effect of it not being there, I am not sure. Its presence would ensure that a supply of oil remains in the tunneling from oil pump to big end bearings should the engine be left unrun for any length of time. The same thing would however occur anywayif it were not there as the drain-through / wet sumping properties of the oil pump would ensure a supply of oil along the same route, eventually filling the sump. Most likely explanation therefore would seem to be that it is intended to be a built-in anti wet sumping valve as it would only open with pressure from a working pump. Given the volumes that have been written on wet sumping and oil taps it seems surprising that no mention of this.

The above my inexpert guess, any more informed opinion appreciated.

Many thanks indeed Paul and congratulations on solving this conundrum. The embedded ball valve shown in the photo of your timing case cover is exactly as I recall seeing in my 1957 19S engine and my 1959 ES2, it was clearly a standard fitting in later ohv models. I see now that the part numbers you list are indeed included, although not illustrated, in all Parts Lists from 1957 until the end of singles production.The 1957 list shows the same numbers, total costing then just 14 old pennies !

The 19S engine I am presently working on is 1955 and wouldn't therefore have been fitted with this valve, the little brass widgetthat I foundis likely a DIY item that shouldn't be there and will be discarded as I fit a Mick Hemmings anti-drain valve to all my post-war Nortons.

Mystery solved, well done ! What a useful technical forum if you hang on long enough !