Ring Gap Calculator

Liguori Drag Racing / Engine calculators

Ring Gap Calculator

Choose your ring design, fuel and application, then enter the finished cylinder bore. Use custom mode when your piston or ring kit specifies different factors.

Measurements Top-ring designChoose the design of the top ring, even if your second ring is gapless. Fuel group Engine applicationNitrous bands use added nitrous horsepower. Boost is gauge pressure. Guide ranges overlap at endpoints; use your ring kit instructions to choose the band. For combined boost and nitrous, use custom kit-specific factors. Finished cylinder bore (in) Oil-rail minimum gap (in)Preset oil-rail minimum is 0.015 in (0.381 mm). Expanders and support rails follow their own kit instructions. Top-ring gap factor (gap / bore)Preset factors fill automatically. Select custom mode to edit. Second-ring gap factor (gap / bore) Measured top-ring gap (optional, in) Measured second-ring gap (optional, in)

Choose your application and enter the finished bore. Opens in US Standard.

Application factor guide

Application	Top factor	Second factor	Oil-rail minimum

Calculation method & limits

Top- and second-ring gap = finished bore × selected factor. The same factor works with inches or millimeters. Oil-rail minimum is a fixed gap, not a bore multiplier.

These are general application guide values, not absolute specifications or approval for every piston, ring material or engine. The instructions supplied with your exact piston and ring kit take priority. Tune, fuel, operating conditions and combined power adders can change the required gap. Use custom mode for combinations outside the guide.

Measure each ring squarely in its intended finished cylinder. Results are rounded for display; do not round a specified minimum downward. Being above a guide gap does not establish an acceptable maximum. Follow the separate instructions for oil expanders and support rails.