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These are the minimum recommended ring end gaps, per inch of bore, as recommended by JE Pistons. Other piston or ring companies may offer slightly different recommendations. Per this chart, a 4.500-inch-bore big-block Chevy that will see moderate nitrous would need a (4.50 x .005) = 0.0225-inch top ring gap and a (4.50 x .0055) .02475-inch second ring gap, rounded to .025 inch.
You may also notice that the second ring gap is recommended to be slightly greater than that of the top ring. Not all that long ago, accepted practice was to tighten the second ring gap over the top ring’s. However, testing has revealed that increasing the second ring gap relieves pressure buildup in between the top and second rings, which can partially unload the top ring and induce leakage.
Keep in mind that the primary job for the second ring is not to seal compression but instead to squeegee any remaining oil off the cylinder walls left by the oil rings. It’s is the second ring’s
secondary job to help seal cylinder pressure.
From JE Pistons website
