Finally, a block must often be decked to achieve the proper deck height. Deck height is the distance from the crank centerline to the deck surface. Normally, the deck height is established just a few thousandths above the piston top when it is at TDC. Manipulating the block's deck height helps dial-in compression and also ensures the proper quench area. Quench is when the piston comes within around 0.060 to 0.045 inch of the deck of the head (this includes the thickness of the gasket). Proper quench area promotes good mixture motion of the air/fuel charge and more efficient combustion. Whenever you make a change in deck height, you must also make sure that there is still sufficient piston-to-valve clearance. Decking a new block usually costs an average of $150.

Decking is the process of cutting down the portion of the block to which the cylinder heads mate. This is important for several reasons. First, it is often necessary to remove some material from this part of the block just to "square up" the cylinder heads. The deck of the block must be perpendicular to the crankshaft centerline. In a V-8, the decks on both sides of the block are at 90-degree angles to each other. A block should also be decked to ensure a good, flat surface so that you can achieve a good gasket seal.