When removing the spark plugs on a White and Poppe engine it is not unusual for the valve cap to unscrew rather than the plug. The reason for this is two fold. First the caps are never that tight as a special tool is needed to do the job properly. People usually resort to a chisel and hammer (see the witness marks on the above cap) or a pipe wrench!
The second reason why the caps unscrew is that the plugs are locked into the cap by a carbon build up. The plugs actually extend past the surface of the cap and this leads to the plug being sealed in very tightly.
The first task was to make a locking tool. This has the ears on one side to engage with the cap and a 1" AF hex on the other side for a big spanner.
New copper sealing rings are needed under the caps and although ebay can provide most things, White a Poppe copper sealing rings are even beyond ebay. These can be made from parting off 3" copper bar/tube in a lathe or made from 1.6mm thick copper sheet. The rings can be profiled from the sheet in a number of ways. Although laser cutting is possible, most laser cutters do not like copper and the cut edge has rags with molten copper deposits. Water jet cutting is viable, but the method I chose to use (Electrical Discharge Machinig -EDM) is the most precise. In this process a spark from a continuously moving wire erodes the material away by an electrical discharge. The wire never actually touches the material so that absolutely no cutting forces are applied. This is perfect for thin materials with little strength. The picture above shows a stack of 8 sheets which have had the central circle removed, The wire started from a hole in the centre of the sheets, moved to the inner diameter and then proceeded to cut the inner diameter.
Here we see the outer diameter being cut. The wire is 0.25mm thick.
A complete set of burr free highly accurate copper sealing rings. Should I have made them as how they made them in 1913, well I neither have 1913 technology or 1913 skill!