The reason for the angle of tilt was to keep the timing bush oilway at the base of the bush vertical. This was then used to check the non return valve which is on the opposite (inside) side. The valve was removed and cleaned thoroghly and a new 1/4 ball bearing and spring reseated before assembly. The oilway was then filled with thin oil and left to see if it remained in the valve and not leaking out past the seated ball bearing seal. The valve worked so the retaining grub screw was loctited into place.
The observant might notice that some bushes/bearings should have been fitted into the heated case before the valve was assembled. However, wear means that with the exception of the sleave gear bearing in the gearbox all other bushes were a tight hand fit, with a tap at the end to seat, and all have to be loctited into place on re-assembly. This means the only heat required is at the gearbox end to fit the bearing and as this will be fairly localised it should not effect the non-return valve. I would like to have made a set of slightly oversize bushes throughout but have no access to a lathe and need to keep the engineering favours to a minimum as I need to convert the timing side bush later, and get the small end bush reamed while still attached to the crank.