papaindigo wrote:
As far as I know there is no block drain plug. In fact I don't recall a coolant drain plug on the block of any engine I've ever worked on; the drain plug is on the radiator.
That said I would imagine you could plumb the inlet and outlet of an aux heater into one of the coolant lines on top of the engine. Perhaps the one on the driver's side that feeds the EGR cooler.
Any particular reason you are adding an aux heater? I'll admit it doesn't get that cold here, mid to upper teens F, but the stock block heater seems to work quite well.
Your comments are very strange, Papaindigo. Every engine I have ever worked on
has a coolant drain plug for the engine block.

I will try in my spare time to find an R428 engine at a wrecker so I can get a good look at it outside of an engine bay. I need to plumb the inlet hose to the auxiliary heater from as low a point in the cooling system as possible to avoid cavitation, and then plumb the outlet hose from the auxiliary heater to as high a point on the cooling system as possible for good heating efficiency.