Yes, the heater replaces a freeze plug and the heating coil is in direct contact with the coolant. The coolant slowly circulates by gravity and the entire engine will eventually warm up if given some time.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy