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Poly History.....Dodge block versus "Plymouth" block

From: Hank Dozier
Remote Name:
Date: November 14, 2002
Time: 07:27:35


Kenny...The two engines, although both "polys", are completely different. The Dodge block started as a hemi at 241 CID, and for Plymouth in 1955 got a set of single rocker heads (the poly-head) to keep the Plymouth costs down. This engine was the original "HyFire" engine. Then as displacements increased, the poly versus hemi head combinations proliferated. The Dodge was built in displacements of 241, 259 (poly only, also called a 260), 270, and as a raised-deck engine block in 315 and 325 displacements. ALL these versions had poly-head and hemi-head versions, except the noted 259, which was a poly-inly build. More 315s and 325 were poly than hemi, and that was because Chrysler was trying to reduce its engine costs to compete with Ford and GM. NOW...The "Plymouth" poly. This engine was designed by Chrysler Canada originally as a lower cost truck engine for Canadian Fargos and Dodges. Even before it was produced, this philosophy changed (economics again) to put it into Canadian-built Chrysler products. It is distinguished from the Dodge block by the fact it has a "closed" valley. The intake seals off the lifter gallery instead of a seperate cover. This engine is also known as the "wide poly" due to the fact it had a much larger bore capacity in the block. Displacements for thsis engine were 277,301, 303, 313(Canadian only), 318, and 326 CIDs. The first US application was the 1956 FURY, which got a 303 engine with a WCFB 4bbl. This engine became the "A" block 318 that was the direct predecessor of the "LA" series of MOPAR engines. It was made ONLY in 318 displacement after about 1960, and was produced in the US through 1966 (1967 in Canada). This is the engine that MOPAR Muscle magazine did the hop-up on. There are aluminum 4bbl, 2x4bbl and 3x2bbl manifolds out there that fit it, as well as the iron 4bbls and 2x4bbl "Super Fury" manifolds of the late 50s. It can be quite a performer (so can the Dodge polys), but not a lot of speed stuff was developed for it, since all the attention was given to the "Max Wedge" program and engines by Chrysler.


Last changed: July 19, 2018