HomeResourcesPiston and Ring GapPiston and Ring GapPiston to cylinder wall clearancePlease read the specification sheet provided with your pistons. Piston diameter must be measured at the gauge point indicated in the diagram. Required clearance depends on diameter, alloy, type of forging (full skirt or slipper), application, operating conditions, etc.Recommended Ring GapIt is important to recognize that some end gaps for individual engines may vary from this standard because of engine manufacture’s requirements, type of application, fuels, etc. The top ring gap should be as small as possible to avoid blow-by. The table appearing below is for reference only.Top RingMultiply the Bore diameter in inches by the following factor: (if diameter is in mm divide by 25.4 to convert into inches) Application Factor Street Performance 0.0045 Moderate Turbo/ Nitrous 0.0050 Drag / Oval track 0.0055 Turbo / Nitrous Race only 0.0065 Second RingMultiply the First Ring Gap x 1.25Oil Ring GapMinimum Gap 0.015”Wire Locks installationInsert one end of the lock into the groove and continue spiral feeding until de lock is fully seated.Oil Ring installationExample: Subaru Oil Ring with rotational locking detent The Oil Ring Side Rail are supplied with one or two tabs: One is to lock the rail using one of the grooves in the piston and is installed with the tab facing the side of the groove. The other tab (if available) is to lock the middle expander. Use at the bottom or at the top (is the same). Install the middle expander with end gap about 90 degrees from the wrist pin centerline. Locate the upper notch in the oil ring groove. Install Lower Oil Ring Side Rail and rotate it until the tab falls in one of the oil grooves oposite to the upper notch. Install the Top Oil Ring Side Rail rail and rotate it until the tab falls in the upper
