1932 Big 4

The earliest part list that I have covers 1933 - 35 models and shows the valve, inlet and exhaust for Models 1 and 16 to be part number 9120 and this number continued for civilian models up to 1937 and for WD16Hs until the end of production in 1945. 1938 - on civilian models are different as are WD Big 4s.

In his Norton manual, Edgar Franks states that there were "no engine modifications introduced for the 1933 season which affected maintenance instructions..."

Is your engine definitely a 1932 model ? If manufactured from September 1932 onwards then it is likely to be a 1933 model in which case you have no problem as WD16H valves are widely available (I'd recommend G&S Valves in the UK)

If you're in any doubt, it might be worth posting a photo of the existing valves here together with dimensions.

Svein, the 16H valve is certainly not the same as you have so if you have original and not adapted valves then they are not identical.

The 9120 valve has a stem diameter of 8.6mm - 11/32"

Stem length is 128.95mm - 5 5/64"

Head diameter 41.36mm - 1 5/8"

Sorry that it's not a lot of help.