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Most aftermarket rings must be filed down to achieve the proper gap. Electric filers make the job easier, but manual filers work great as well. For naturally aspirated street/strip engines, a gap of 0.0045 inch for every inch of bore is recommended for the top ring, and 0.0055 inch for every inch of bore on the second ring. That equates to a 0.018- and 0.022-inch gap on the top and second rings, respectively, on a 4-inch bore motor. For nitrous and forced-induction applications, a larger 0.0050-inch gap per inch of bore is recommended. These are good rules of thumb, but different piston manufacturers have different guidelines, so it doesn’t hurt to check with them directly for their recommended gap specs.