Grey Motor Welch Plug sizes

[EffCee]

Hi
I was wondering if anyone could tell me what the sizes of the welch plugs were in the Grey Motors. I know the earlier engines had two welch plugs that were fairly small and the later engines had three welch plugs that were the same size if I recall correctly. If I am correct there were still later engines that had three welch plugs fitted but were larger than the previous Grey Motors. I used to race speedway 25+ years ago and cannot remember for the life of me what engines came from what. ???

I think that the early two plug blocks were 48 series and early FJ, the smaller three plug blocks were later FJ through to FC or FB and the grey motors with the larger welch plugs were fitted to eiter the FB or EK and EJ. Can anyone tell me if I am correct..... ??? and what the sizes of the welch plugs are.