Nobody believes what magnesium can do when catching fire...in dust, it is like gunpowder. In a VW block...even the Sunlight pales ! Some dudes here in México, WELD the damned things (& with success!)...they crack usually at the oil cooler base.
Summer time...1978 - At the VW factory in Puebla México, two young "campesinos" from Tlayacapan Morelos, got a job. For mopping floors until better trained. They started their mopping, near the shop machining the blocks. Magnesium when drilled, has the chips coming out redhot & sparkling all over the floor. Like the Bengalas for children, at their birthdays (well, here in mexican birthdays).
So the young campesinos, to proove their worth and good intentions (& to earn a better income) tryed to put them out...throwing at them their buckets full of watter. Five people there, were icinerated instantly. NOTHING was left, nor even a shoe...it's the worst you can do for putting out magnesium (if the heat lets you go near it!): adding watter !!!
Thery have a better trainig section at the VW mopping squad, now.
P.D.- The VW aircooled Beetle block, was a Magnesium alloy, with a slight amount of aluminum, phosphor & tin added. That formula is a secret of state, Achtung!