Originally designed in 1968, the 6-liter Chevy 366 was a popular engine for Chevy & GM’s medium-duty trucks and school buses. Variations of this engine remained in production until 2004, though fitment is different for each iteration.
Throughout its life, the 366 included 4 rings on the pistons. The 366 is also a tall deck engine, with a deck almost half of an inch taller than the 392, 402, and 454 production engines.