Vote for The Forward Look Network on the Mopar Top 100 Sites 

Re: 55 chrysler 331 engine questions

From: Mike Patterson
Date: March 02, 2002


The wedge engines you refer to are actually Polyspherical Head (Poly) instead of wedge head motors. A 331 can be made into a Hemi by simply changing heads, valve train and manifolds. This also holds true for the 354 Poly (spitfire) and 354 Hemi engines. As the 331 and 354 are basically the same engine except for bore, 331/354 parts are also interchangable. As the Chrysler 392 is a tall deck motor, about the only thing interchangable is the intake (see the posts below about 354/392 Intake manifolds.) Dodge and Desoto Hemi parts do not interchange with Chrysler or each other but will interchange within themselves. Most people tend to overlook the poly motors in favor of the Hemis (the hemi has a lot of visual appeal and does make more HP than the Polys). The Polys were actually a very good motor and made very respectable horsepower in their own right and had the added advantage of lighter weight. They should not necesssarly be dismissed out of hand.


Last changed: July 19, 2018