This is not unusual because many (but not all) production engines place the piston deck below the block surface. With a small-block’s deck height listed as 9.025, this appears to put this piston 0.025-inch below the deck. We looked up a typical 350 piston with a 5.70-inch rod and found compression height listed as 1.560 inches.
This is then subtracted from the engine’s deck height to find the deck clearance, which can be positive (above deck) or negative (below deck). The simple math calls for dividing the stroke in half (3.48 / 2 = 1.74 inches) and then adding the connecting rod length and compression height. This leaves the last variable as piston compression height. Our example uses a 9.025-inch deck height, along with a 3.48-inch stroke and a 5.7-inch connecting rod. Let’s use the classic small-block Chevy 350 as a case study. While perhaps not accurate to 0.001-inch, it is an easy way to determine whether the deck is square.Īll of this is important if you want to add stroke to the crankshaft to increase displacement. This calculator will compute the deck clearance for above or below deck applications.įind the engine displacement based on stroke and cylinder measurements.A simple way to check deck height variation is to measure the piston position relative to the deck using the same piston and rod on all four corners of the block. Use this calculator to get the approximate piston compression height. Using this calculator, you can obtain the proper ring end gap requirements for KB Pistons using end gap factors from inside the front cover of the KB catalog or on this website in the tech article titled "Special Clearance Requirements for the KB Piston." This calculator will give you the proper piston head volume with a known compression ratio.Ĭonvert inches to millimeters or millimeters to inches. (considers cam timing and rod ratio) This calculator will give you a dynamic compression ratio taking into account cam timing and rod ratio. It will also estimate a dynamic effective compression ratio taking into account the cam timing and rod ratio. (considers cam timing and rod ratio) This calculator will give you the proper compression ratio with a known piston head volume. When this happens the valve reliefs and the pop-up are approximately equal in value. On the piston calculator many times you will come up with a piston head volume that approaches zero. If you do not have the exact gasket bore use the cylinder bore in its place. With some pistons this flat area may be very small (example: Chrysler Hemi is only a line at zero deck). Do not measure to the top of the pop-up or the bottom of a dish. Deck Clearance.Deck clearance should be measured from the top of the block to the flat portion of the piston.Located above each picture in the KB Catalog is the value for the piston head volume shown in positive or negative numbers. Pistons with a dish or pistons below deck increase chamber volume and receive a positive value. Pistons with pop-ups or pistons sticking out above the deck will reduce chamber volume and will usually require a negative number. Negative numbers indicate a reduction in cylinder head volume.
Values for Piston Head Volume and Deck Clearance can be entered as both positive or negative values.
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