NH 350 Oil Pump case differences

[T Batnes]

On my W/NG, which is a 1940 with a 1943 engine in it, there's this timing cover

It's clearly of the pre war design with a pressure regulator above the rocker oil feed banjo, so probably fitted to the engine as a replacement for the original item. Also, there is no spring loaded ball valve fitted to the main oil feed hole behind the pump, as on the cover on the other post in this thread. So, as I understand it, I don't need to fit this one way ball valve, as the adjustable regulator valve on front of the timing cover does the same job, and takes care of delivery and pressure to the rockers? Is it so? Why did they change this design?
Engine no is RBH25216, frame no is XG13126.

[alan.moore]

On my W/NG, which is a 1940 with a 1943 engine in it, there's this timing cover
It's clearly of the pre war design with a pressure regulator above the rocker oil feed banjo, so probably fitted to the engine as a replacement for the original item. Also, there is no spring loaded ball valve fitted to the main oil feed hole behind the pump, as on the cover on the other post in this thread. So, as I understand it, I don't need to fit this one way ball valve, as the adjustable regulator valve on front of the timing cover does the same job, and takes care of delivery and pressure to the rockers? Is it so? Why did they change this design?
Engine no is RBH25216, frame no is XG13126.

So your inner timing case looks like this ? :

early timing case exterior pressure valve.JPG (95.12 KiB) Viewed 2303 times

If so then YES the adjustable valve does the same as the later one fitted behind the pump. If you undo the valve there should be a ball bearing, a piston and a spring.
The change took place in 1941, I expect that the later behind pump plug, ball and spring were more cost effective to produce than the external valve.

Here is another post that may help

http://forum.arielownersmcc.com/viewt ... 7&start=20

It is very interested that your engine number is RBH....there is information that Ariel prefixed some of the WNG engines with a R for engines going to the RAF and N for those going to the Navy but I think they are pretty rare

Cheers
Alan

[T Batnes]

Yep, looks exactly like that. Possibly the crankcase only has been swapped, and the "external" bits have been reused when the bike got the replacement engine. As it seems, a lot of W/NG's were sold off to Norway after the war, this was one of them. But, as some were in a bad state after up to five years of service, they got rebuilt with bits and pieces from other bikes. So it probably got a crank case from a written off '43 RAF bike in '45, before it was sent off to Norway. It has a civilian registration history in Norway all the way back to 1948. Between '45 and '48 I don't know, possibly been used in the armed forces. Here's the bike, now pulled to bits for a restoration.

[T Batnes]

Engine no.

Frame no.

[alan.moore]

Very nice example

[T Batnes]

Better pictures of the engine and timing cover.

[alan.moore]

My 1939 VH has the date 25 4 39 cast into the timing case under the part number A7/507 and it looks as though yours is the same. I assume this must be the date the casting mould / die.

[nevhunter]

Those casting numbers give you the "earliest" date the particular PATTERN was used. it still could be machined up in a different way, later on and have a different part number. The later set up eliminates some areas of oil leakage, and would have been a possible replacement in service also on an earlier model. When these things were refurbished and sold after the war, anything could happen. Matching numbers etc didn't have much/ any significance. NOS and old bits were used as available. to feed the market. Nev