internal or external balance

According to my MOPAR PERFORMANCE A-engine book.

All 318's from 1968 to 1992 have cast crankshafts but are also internally balanced.

The 340 with the same stroke is externally balanced with a cast iron 3.31" stroke crankshaft, because it has heavier rods and pistions than the 318. Forged steel cranks are made of denser materials than cast cranks, this allows for internal balancing with higher piston/rod weights.

ALL 318's are internally balanced period.

Bob