Squish Question
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Teching In
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From: San Jose CA
Squish Question Please foward to the right forum if this is the wrong one.
My understanding is that squish has to do with calculating the flat part of the piston, if the piston was dished, one would calculate as if it were flat in regards to the deck, head, and gasket. The tighter the squish, the more performance. Here is my question, my pistons have two relieve valve holes cut into them, so I was thinking, could I actually run a tighter squish, say.020, and not even have to worry about the pistons kissing the heads. Or this is asking for trouble. .007 out of the hole with a custom gasket at .027. This would be a cold squish on an ls6 block.
My understanding is that squish has to do with calculating the flat part of the piston, if the piston was dished, one would calculate as if it were flat in regards to the deck, head, and gasket. The tighter the squish, the more performance. Here is my question, my pistons have two relieve valve holes cut into them, so I was thinking, could I actually run a tighter squish, say.020, and not even have to worry about the pistons kissing the heads. Or this is asking for trouble. .007 out of the hole with a custom gasket at .027. This would be a cold squish on an ls6 block.
.020 isnt gonna happen, the valve pocket has nothing to do with squish, also known as quench. The quench area is the distance between the flat edge of the piston and the head deck. The valve pocket does not give you more room between the piston and head deck. Do not even attempt .020 unless you have a highly precise machined rotating assembly like in a straight up race car. I mean very tight tolerances too because any rock in the piston will have a high chance of causing the piston to rock into the head deck.
Thread Starter
Teching In
Joined: Jan 2005
Posts: 48
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From: San Jose CA
Originally Posted by brad8266
.020 isnt gonna happen, the valve pocket has nothing to do with squish, also known as quench. The quench area is the distance between the flat edge of the piston and the head deck. The valve pocket does not give you more room between the piston and head deck. Do not even attempt .020 unless you have a highly precise machined rotating assembly like in a straight up race car. I mean very tight tolerances too because any rock in the piston will have a high chance of causing the piston to rock into the head deck.
If you really wanted to push things that far the best way to do so is to get actual measurements. Taking the heads off of the car and claying everything. I think the forged aluminum expands around .015, but this is just a guess. You can actually calculate this by looking up the material properties, such as expansion rate according to operating temperature. Honestly, is the risk worth the power you are going to gain out of 0.015" of quench difference?
