If I take the same pic and sit a flat metal ruler across the top would that help indicate the gap easier? What make or style of plug is the one you use then?
The spark plugs are just B7ES instead of BP6ES. 7 is the heat rating of the plug, so that is increased by one point and the lack of P in the part number shows the plug is not the protruding tip type. This is NGK numbers which will differ from other manufacturers. In competition use I have used a B8EVX which is another heat range up, and platinum fine electrode tip. Same plug they use in the higher spec Ford crossflow engines. Not that expensive for plugs.
Easy, I am Scottish, I cannot stretch to iridium as that leaves very little left over for the drink! I work on the base that if I rev it hard enough, the plug will stay clean. You could use a BC..... type plug too, the C denotes the smaller sparkplug socket size. Makes no odds really, but a lot of the newer cars use this style so you may find them listed cheaper.
