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Old 11-21-2012, 10:47 PM
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Originally Posted by mouse77 View Post
Your gonna confuse the poor kid with this talk of the quench myth.
You cant calculate "quench" effectively when you are using a full dish piston, the "quench" is essentially the entire combustion chamber with those pistons.
Perhaps the raised ring on the piston, (Probably almost .030 in the hole with an unmachined deck) Might be closer to .070 "quench" (.030 in the hole, stock style .038 gasket), but still will be very low compression.
The 330/350 horse GM crates with a very similar piston, and vortec heads are 9.0 to 1.
I believe the "poor kid" can- if he wishes to- grasp these concepts just fine.

In order to give any meaningful CR estimate there has to be solid numbers to work from. The "raised ring on the piston" as you call it (actually this is the piston deck) to the block deck is where the quench (quench/squish, or "squench") measurement is taken. Without having a point of reference there can be no actual CR measurement; it would be a range, like between 9:1 and 9.2:1.

Now, I do not pretend to think that in this case a variance from 0.040" quench of + 0.010-0.015" will matter all that much. But beyond that it sure DOES matter as to how the engine will tolerate lower octane fuels and/or other less-than-ideal operating parameters when it comes to detonation- even w/a round dish piston. Actually it probably matters more w/a round dish piston because it has such a poor design for giving good quench action compared to an inverted dome type piston.

Take a look here for more on the concept, as well as a disambiguation of the word "quench", quench and squish being two entirely different things).

That the round dish piston has a less than ideal configuration for producing good quench action is well known- that's why a D-shaped or inverted dish piston is preferred when a dished piston is required.
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