Head Gasket Thickness / Quench

Now that we have Cometic MLS Head gaskets for these engines, there are more choices to be made.  The main focus of questions has been the compression ratio possible with thinner gaskets.  This is a great idea, but depending on your engine, it could work against you as well.

The following is copied from http://www.theoldone.com/archive/quench-area.htm 

Quench, or squish area is typically the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.
If you look at a combustion chamber, you will usually see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.
The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the "quench" comes from.
When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios, and due to this they are considered "artificial octane" by scientific types.
Bottom line is "properly designed, quench is good". 

Taking the stock 3400 for an example, we have a piston that has a flat area around the outside, and a heart shaped combustion chamber on the head with lots of flat area around the outside.  This is a great design to put the mixture into the center of the cylinder.  The stock piston sticks out of the block .020" and the head gasket is .060" thick.  This leave .040" between the top of the piston and the surface of the head.  .035-.045 is considered optimal quench distance, depending on the RPM you intend to run.  For 5000 RPM on stock forged connecting rods, .035" is enough space.  For 6000-7000, .040" is enough.  Past that and .045" should be used.  The reason being that connecting rods stretch at higher RPM.  You must account for the stretch or there will be a greater possibility for piston to head contact.

For custom pistons, the piston height can be adjusted easily and either the gasket or head can be changed from a stock spec to give the beste quench.  For stock engines, the following should help you choose your MLS gasket thickness

3100 - Piston sticks out .020".  Head Gasket should be .060" thick (Stock)

3400 - Piston sticks out .020".  Head Gasket should be .060" thick (Stock)

3500 - Piston sticks out .010".  Head Gasket should be .050" thick (Stock is .060")

3.4 Iron Head - Piston sits .010" below deck.  Head Gasket should be .030" thick.  Compression will be increased but no problem on iron heads.  Compression will be in the 13:1 range using 3400 heads.