When you see a Poly Head engine for the first time you will probally ask yourse
lf " WOW what in the world is that?"
The Poly Head engine is a logical extension of the famous Hemi* head engine of
the Chrysler Corporation. Logical in the sense of cost and weight.
Cost was reduced by using only one rocker shaft per head, and spark plugs were
mounted ouside of the valve cover, reducing the need for spark plug tubes. Anot
her cost saving feature was that the combustion chamber was cast and not machin
ed like the early Hemi engine. Weight was reduced by eliminating the huge casti
ng needed to support the second rocker arm shaft.
Below is a image of a Poly cylinder head. The area in red is the partial surfac
e of the valve cover seat. Notice the waviness of edge. This is the external ch
aracteristic of the Poly head. No other engine valve cover has this outline.
Below is a 270 Cubic inch Poly head engine
Below are images of a cross section of the poly head, and hemi head. Notice the shape of the combustion chamber on both. Also take notice of the spark plug wi re location, the rocker arm shafts, the location of the valves, and the angle b etween the valves.
* Hemi = Hemispherical
For more information on th Poly head visit the Polyspherical Engine Association
