Mopar Action On-line – Tech Questions
leo mangin, essex, ON , canada, 67 cuda plymouth convertible 273
What is the difference between the 273 and 318 or 340, 360small blocks? Will parts fit between any or all of these engines?
Complex answer. I’ll narrow it down to pre-’92, non-poly engines:
Basically, they are all the same family (LA)
All have same length connecting rods and basic block dimensions,distributor shaft, exhaust flange bolt pattern, clutch hsg. pattern, deckheight and deck pattern, etc.
Bottom end is significantly different on 360s (main journal diameter andmaincap bolt spacing). 360s have longer stroke (3.58″) than all other LAengines (which are 3.31″)
273 and 318 have cyl head smaller ports.
Pre-70 has different front components.
All 360s and 72-1/2-up 340s are externally balanced.
Early 273s use different intake flange bolt pattern.
340s and 360s have a different left side mounting ear configuration.
Subject to the above, many, many parts will swap, but it a mistake to thinkthere is 100% interchangeability.