[marcin]

The combustion chamber shapes are different. The d16z6 has a hemispherical shape and the d16y8 combustion chamber is squared. The d16z6 combustion chamber holds more volume than the d16y8. Because of the d16y8 smaller combustion chamber, the head yields higher compression than the d16z6.

hey, just a note, d16z6 is not a hemispherical chamber but rather pent roof. the y8 is also but with different quench design



m.

 

[marcin]

it is not hemispherical, they are both pent roof designs. look up the defenitions gentlemen.

m.

 

[marcin]

.

i will list links below the text
source:http://autorepair.about.com/library/glossary/bldef-265.htm
pent roof
Definition: A combustion chamber whose upper surface resembles a shallow peaked roof. Usually used with four valves per cylinder.

source: http://auto.howstuffworks.com/hemi1.htm

In a HEMI engine, the top of the combustion chamber is hemispherical, as seen in the image above. The combustion area in the head is shaped like half of a sphere. An engine like this is said to have "hemispherical heads." In a HEMI head, the spark plug is normally located at the top of the combustion chamber, and the valves open on opposite sides of the combustion chamber.

more from how stuff works
One thing that a hemispherical head will never have is four valves per cylinder. The valve angles would be so crazy that the head would be nearly impossible to design. Having only two valves per cylinder is not an issue in drag racing or NASCAR because racing engines are limited to two valves per cylinder in these categories. But on the street, four slightly smaller valves let an engine breathe easier than two large valves. Modern engines use a pentroof design to accommodate four valves.


hemi history
http://auto.howstuffworks.com/hemi.htm
more history stuff
http://www.allpar.com/mopar/hemi/ardun.html

 

[marcin]

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looking at a high comp piston from both a Hemispherical and pent roof design head might help too.

pent roof
sourced from theoldone.com

HEMISPHERICAL