The modern rendition uses two "squish pads", one each to the front and rear of the chamber; this helps keep the air-fuel charge closer to the center of the chamber and encourage additional turbulence. Ideally, a combustion chamber would resemble a sphere, as this results in the least surface area for a given volume (that means less heat rejection to the coolant) and the smallest burn distance for a spark plug. Domed pistons in a hemi chamber results in a thin skin of charge; imagine a golf ball sitting next to an orange rind and you get the idea. The squish pads improve the situation significantly, with the only drawback being semantics regarding the trademark name. Squabbling about the chamber shape neglects the most important attribute of the Hemi design - the valve placement.





Note the complex intake manifold geometry. The large plenum and long runners help maximize the torque across the rev range and help the engine to come on strong right off idle without excessively compromising upper-end power.



The angle of the valves allows them to travel towards the center of the cylinder and away from the cylinder walls. This helps prevent the phenomenon of "shrouding", where a portion of the valve becomes ineffective. Due to this, the flow of Hemi heads is quite impressive across the full range of valve lift.










Barely visible here are the oil squirters that keep the pistons cool. This is certainly not a typical feature for a mass-production domestic V8.

This particular cross-section of the head shows the twin spark-plug bores.