How to Measure & File Ring Gapįirst, install the individual ring into a specific cylinder (we typically begin with cylinder #1 in the engine firing order). State of engine tune, operating environment, and personal experience should also be considered. Total Seal notes that these are general gapping recommendations and should not be considered absolute. The following is a recommended gap chart for conventional (gap style) rings from Total Seal Piston Rings: Street, strip, circle Some second ring sets can be set slightly looser, but that depends on the ring configuration and the manufacturer specs. Adding nitrous or boost (turbo or supercharged), or building a combination that runs abnormally hot, will affect the gaps. As a basic rule of thumb, a gap of 0.004-inch of end gap per inch of cylinder bore diameter is a good place to start. Most folks say the gaps on the second ring are driven more by the cylinder bore diameter. In reality, there isn’t just one answer to that question. The top ring gap will change based on the amount of heat introduced into the engine. So what’s the correct ring gap for your engine? Running with ring gaps butted will result in scuffing of cylinder walls and/or flaking of moly from the ring face.”Īs you can see, getting the gaps right makes more power. Examination of the rings indicated that the top rings were butting. In this final test, the results again showed a reduction in blowby but a noticeable loss of horsepower was observed at higher speeds. An additional test was made with the top ring gaps set to 0.010-inch. In the second test, top ring gaps were reduced to 0.016-inch. The baseline test was run with top ring gaps set at 0.024-inch. Blowby was reduced by approximately 50 percent, and horsepower increases ranged from 5 to 13 percent. “Comparative tests using a 350-cubic-inch small block Chevrolet engine reveal definite improvements in blowby control and horsepower as top ring end gaps were decreased. Too small a gap, and the ring ends will butt together as the engine heats and expands. This can damage your engine.Īccording to decades-old Speed Proresearch (which is still valid today): Too large a gap, and cylinder pressure leaks through the gap and the engine loses power. The reason a compression ring is file-fit in a high performance engine is because the gap affects performance. Even in file-fit ring packages, the oil ring package is simply installed as delivered by the manufacturer (we’ll get to this later). This only applies to the top and second rings in each ring set. By design, it’s up to you to measure and set the end gaps. Typically, file-fit rings are designed so they measure 0.005-inch oversize (obviously larger than the cylinder bore size). And many of these ring sets are designed to be hand-fit to each cylinder bore. When you shop for high performance piston ring sets, you’ll no doubt find there are many different sets and styles available (no big secret).
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