headbolt heater

• head-bolt heater
• head bolt heater

headbolt heater (plural headbolt heaters)

1. A form of block heater that consists of a hollow headbolt which contains an electric heating element.
   • 1949, American Railway Engineering Association, Bulletin - Issues 481-487, page 277:

     The headbolt heater consists of a hollow steel bolt containing an electric heating element. This device is designed to heat the water jacket and is applied to the engine head by replacing a headbolt.

   • 1969, Jeno F. Paulucci & ‎Les Rich, How it was to make $100,000,000 in a hurry:

     Second we were told that the company in all fairness, with winter almost on us, should provide headbolt heaters for employees' cars in the parking lot. A headbolt heater, in case you don't know about life in the frigid zone, is a gadget that you plug into a parked car. So if it's forty below that day, your car will still be reasonably warm when you're ready to go home. It might even start.

   • 1994, Dana Stabenow, A Cold-Blooded Business, →ISBN, page 58:

     Plugging the bus into the headbolt heater on the rail, she collected the pup's body from beneath the driver's seat and followed Toni into camp.