Famous retired Chrysler engineer
Pete Hagenbuch
on Squish and Quench:

quote

What was involved in going from the A engines to the LA engines?

You know I don’t really remember any problems, there had to be some but I can’t remember anything serious enough to be worth talking about; even the performance improved by getting rid of the silly polysphere. A wedged chamber does have some advantages. One of the advantages is that you can build in a lot of what we call squish, where the chamber is just part of the cylinder head surface and the piston have a flat area that matches up with it, because squish is why you can run 12 to 1 on a wedge head because without squish you would have to run 9 to 1. It gets the charge moving and mixed, you know moving through the chamber at high velocity which means the flame travel is fast and there isn’t anything left to burn by the time it gets to top dead center where you expect the detonation. Anything that reduces detonation also helps reduce pre-ignition which is catastrophic.

Detonation can lead to pre-ignition because of the rise in temperature. If you are in more or less constant detonation then sooner or later you going to hole a piston, its going to become pre-ignition which means it starts burning the minute the intake valve opens which means that the full force of the combustion is working against the piston going up and things get really hot in there, and aluminum melts at around 1200°.

So the wedge would also be good for emissions then if everything burns cleanly?

Yes it is, and the hemi is not. If you look at our hemi it has squish, a full 360°. That is the feature that a lot of fluff book writers use to jokingly call a semi-hemi. But I think once they have driven one they don’t call it a semi-hemi anymore.

Do you mean the current one?

The current one. (5.7)

The most outstanding thing about the current hemi is we make money on it. We didn’t make money on the others, they were too expensive.
end quote

from

http://www.allpar.com/corporate/bios/hagenbuch-interview2.html