What the ......

[Paul Bryant]

anyone know what This hole is for?

We've all got one .... or two

Engine assembly Jig.

 

[barbagris]

Engine assembly Jig.

Ah the hobbits at play.

 

[jake shaw]

I think the holes are used in the machining process when the crankcase halves are manufactured. Probably for clamping the castings to the machine tool.