Originally Posted by firebird7980
The 60 is under the the rest of the number . What do you mean ch of 1.56
CH - Compression Height - is the distance from the center of the piston pin to the top of the piston. 1.56" is the compression height of a standard 350 piston. Many aftermarket pistons are what's called "rebuilder" pistons, they are only 1.54" compression height, or .020" shorter. The reasoning is that it's assumed when the engine is rebuilt the block will be decked, so making the piston shorter will keep the piston deck height (the distance the top of the piston is below the top deck of the block) will be the same. If your engine is rebuilt using "rebuilder" pistons and the block is not decked, now your pistons will be .020" further "in the hole" (down in the cylinder). That will lower your compression ratio, and add .020" to the squish/quench height (distance from the top of the piston to the cylinder head) which makes an engine more likely to have detonation problems or require higher octane gasoline to prevent the detonation.