I agree 100% with Simon. It has worked well enough for me for over 50 years but you do need to change the rubbers from time to time.

I have sent you a Private Message about your petrol tank.

Paul

I wouldn't use a bolt to block the hole. Just clean the hole out and fill it with a bit of silicone. If the silicone does eventually come out it will do no harm at all.

If you are looking for one of these faces, I have them in stock at AOMCC Gauges and Clocks at £10 + postage. You may also need a new bezel which is also in stock at £7.50.
Paul

As far as I can see, you have it exactly correct. Amazingly enough, they do work. Nominally, they are not fitted to the iron 4G but I had problems with excess oil on my 1937 one, fitted the seal (as you described) and it did solve the problem.

Paul

They are both somewhat on the cheap side, in my view, but might be genuine.

One item which escaped me earlier is that your cam has been modified by removal of the pin on the outer end which drives the oil pump. That tells me that you have a non-original oil pump with higher flow than the original Ariel item. This can be a good thing or a bad thing, depending upon the type ...

We will need an end on view of the cam lobes to be able to identify it. You may find it has a number stamped on the end, such as A6/664, A7/642 or F. Whilst telling us that number may help, it won't if the cam has been modified but we might be able to tell if it has had extreme modification.

Looking carefully at the oil feed bath, the holes for Nos 1 & 2 cylinders are 3/16" diameter, the one for No 3 is 3/8" diameter and the one for No 4 is 1/4" diameter. I am pretty sure that I remember correctly that the holes were different diameters on my previous ohc four.

As far as I can ...

Its as original so don't worry about it. Photo taken just now: