Hi , i hope i am stealing no ones thread, but my motor is in Parts at the moment so i could make some shots:
at first : i don´t know if its possible to drill the head without proper gear, like a milling machine or lathe, cause, it needs to be perfekt orthogonal , otherwise the sealing would be impossible with cooper or aluminium washers. Same for the plug in the main oil-gallery.
All holes ( plug main gallery, head 2x) where drilled 9mm and tapped with M10x1 ( i am from Austria, metric stuff is easier to get)
if you are using Banjo-fittings , you need to get the right Hollow-screws to fit the Banjos, thus giving you the right thread to tap.
The head fins needs to get milled to accept the larger Banjo ( see the Pics, you will get it), also you need to mill the sealing surface, cause the cast will seal not very well.
for the restrictors: 1mm should be a 100 mainjet, but the original restrictors got a filterlike design to avoid clogging, so they where my first choice.
You also need to close the old Oil channel, otherwise the whole mod will be useless... i tapped the head with M6 and sealed the screw with screw adhesive high strength, same at the base , only larger ( M12)
i don´t know which way you choose, but if you take the left side oilplug you will need to do some work to the alternator cover.
my solution for the T-section could be found one page earlier.
never mind my oil-line routing, i don´t use a e-starter anymore.
pics:
Head finished:
Head tapped and milled:
whole:
Plug head:
Plug Base:
Alternator cover: