Installed one of Big Mike's engine block heaters. He advertises it as "ENGINE BLOCK HEATER FOR M809, M939, AND M939A1 MODELS w/NHC 250 CUMMINS - EBH250".
The instructions say it's for Cummins (855 CID) engine series with side plate, which I assume covers our engines. The heating element on my device points aft, probably should have installed it at th middle engine plate as the photo in the instructions suggest, but I couldn't get at it without removing more parts than I was prepared to. Regardless, it works great, temps have been in the teens and the engine is warm to the touch.
