Top Piston Ring Gap
4 bore x 0035 0 14 minimum gap.
Top piston ring gap. As an example on a recent 5 7 liter ls build using stock replacement rings on a fresh standard 3 898 inch bore we measured a top ring gap of 0 025 inch. As well as measuring the ring end gap you also need to take note of whether the ends are parallel to each. Hastings recommends a minimum of 0035 gap per inch of cylinder diameter. X the bore diameter.
A feeler gauge inserted into the ring gap will show you the existing dimension and from there you can make your adjustments. For a street engine multiplying your bore size by 0 004in will give you the top ring gap you are looking for. In order to measure your ring end gap once the ring is located in the bore you need to make sure that it s an equal distance down from the top on all sides or in other words it s square. The flat top of the piston will square the ring in the bore and the best part is this tool costs nothing.
Minimum gap tolerances must be observed in order to prevent the ring ends from butting together as the ring expands when the engine approaches operating temperature. 004 x 4 00in bore 0 016 inch ring gap. For the 2nd compression ring the standard end gap recommendation for most stock engines is typically 005 in. So for a 4 inch bore the standard end gap would be 016 inches.