It’s common when rebuilding an engine to grind a small amount of metal off of the top of the block (the deck) to ensure you have a completely flat surface on which to mount the head. However when you do this you end up changing the distance between the top of the deck and the top of the piston when it’s very highest point in its stroke. The effect of this is to cause the piston to get closer to the head, which in the extreme can result in the piston actually hitting the head.

To compensate for the removed metal I will be using a slightly thicker head gasket. This will raise the head up enough to ensure the proper piston to head clearance. In order to select the correct head gasket thickness I used a dial indicator to measure the piston to deck height.

I started off by positioning the piston at the very top of its stroke and zeroing the gauge on the top of the piston.

By carefully moving the zeroed gauge off of the piston and onto the top of the cylinder I can read the difference in height between the two surfaces. In this case the piston is sticking out of the bore by about 12 thousandths of an inch. I repeated this measurement at various locations around each of the pistons to come up with a maximum piston deck height of -0.013” (negative means sticking out of the bore). Since my desired piston to head clearance is between 0.036” and 0.040”, a 0.051” thick gasket should be just right (0.051 - 0.013 = 0.038).