Ua komo nā ʻenekini 645 series i ka hana ʻana i ka makahiki 1965. I ka hiki ʻana o ka moʻo 567 i kona mau palena i ka piʻi ʻana o ka horsepower, pono kahi neʻe nui; ua hoʻokō ʻia kēia ma ka hoʻonui ʻana i ka lua mai 8+1⁄2 in (216 mm) ma ka 567 series a i 9+1⁄16 in (230 mm) ma ka 645 series, me ka mālama ʻana i ka paʻi like a me ke kiʻekiʻe deck. ʻOiai ua hoʻololi ʻia ka pahu pahu mai ka 567 series, 567C a me nā ʻenekini ma hope (a i ʻole 567 mau ʻenekini i hoʻololi ʻia i nā kikoʻī 567C, i kapa ʻia ʻo 567AC a i ʻole 567BC engines) hiki ke ʻae i nā ʻāpana lawelawe 645, e like me nā hui mana. ʻO ka mea ʻē aʻe, hoʻohana ka ʻenekini 567E i kahi poloka 645E me nā hui mana 567.

Hoʻohana nā ʻenekini 645 a pau i kahi puhi Roots a i ʻole turbocharger no ka ʻohi ʻana i ka cylinder. No nā ʻenekini turbocharged, hoʻohana ʻia ka turbocharger a loaʻa iā ia kahi puʻupuʻu overrunning e hiki ai iā ia ke hana ma ke ʻano he centrifugal blower ma nā wikiwiki ʻenekini haʻahaʻa (inā ʻaʻole lawa ka holo kinoea a me ka mahana wale nō e hoʻokele i ka turbine) a i nā māmā māmā. Hiki i ka turbocharger ke hoʻi hou i ka hana ʻana ma ke ʻano he supercharger i ka wā e koi ai no ka piʻi nui ʻana o ka mana o ka mīkini. ʻOiai ʻoi aku ka maikaʻi o ka mālama ʻana ma mua o nā mea puhi Roots, ua ʻōlelo ʻo EMD e hiki i kēia hoʻolālā ke "hoʻemi nui" i ka hoʻohana ʻana i ka wahie a me ka hoʻokuʻu ʻana, hoʻomaikaʻi i ka hana kiʻekiʻe, a hiki i ka piʻi ʻana o 50 pakeneka o ka horsepower helu kiʻekiʻe ma luna o nā ʻenekini Roots-blown no ka like. hoʻoneʻe engine.