45/70 lead won't penetrate cast iron or aluminum
Well, remember, we're not talking about armor plate or even mild steel. Cast iron/aluminum is pretty weak when it comes to impacts, and the .45-70 hard cast has more momentum and lower likelihood of deflection. Either round into a cast iron block is not going to poke a hole, but break out a rather large chunk of the water jacket. Whether or not the round has enough remaining energy and the alignment is correct to dent or break the cylinder wall is another story, though. Also, if the round hits where there is webbing between the water jacket and cylinder wall, it's gonna have alot more integrity and likely deflect the round.
But from the front of the vehicle, there's plenty in the way before you actually get to the engine block. Transverse mounted engines would be more susceptible, since the fan, water pump and other accesoiries are perpendicular to the front of the car. But you still have to get through grill/bumper, radiator, A/C condenser and, in most cases, a cast iron or steel exhaust manifold before you hit block.
Basically, there are no small arms that could be counted on to immediately stop an automobile engine with one or a few shots unless those shots are very carefully aimed and well exucuted by someone who knows the exact anatomy of that particular vehicle. Put that vehicle in motion and take away a stable shooting position (prone, bench, etc.) and the odds of success are drastically reduced.
And again, none of the hypothetical discussion of stopping the engine addresses stopping the
vehicle. To do that with a projectile, it's gonna have to be Gustav or Dora, or a 16" battleship gun, etc. Even a 155mm long tom would not stop a passenger car in it's tracks.
...Target driver,driverside tire,passenger side tire.In that order.
Wait for it,wait for it...JUMP and TUCK.Hope it works.
