I just don't want to see pics of a smoking hulk after a job gone wrong
The ground is usually handled through the engine block, which does need
a ground strap from the battery or from the frame is some cases.
a non grounded engine can get it's grounding needs through odd places
like through the bearings in the axles and up the driveshaft or through the
transmission parts, generally not good places to put volts and amps through,
could cause arcing of the surfaces of the bearings and races or
you just
really never know what electricity is going to do.
Wild