Question: what is a 318 poly engine?
Answer: From 1957 to 1966, Dodge made the 318 polyspherical engine, or the 318a. It was modelled on the popular Hemi engine. The Poly differs in that it is a small block and its heads are polyspherical rather than hemispherical1. ... This increases power and cools the engine. The main advantage of the Poly over the Hemi is weight.