Tedster (9/19/2019)
Ted, do you have any advice on ring gap? I find this kind of thing interesting. There is a debate with some on whether the top ring should have a slightly tighter gap than the 2nd ring or, the reverse also has its enthusiasts. There are arguments for both, apparently.
Always use the manufacturers’ recommendations for ring end gaps before experimenting. As a general rule for stock width rings, I’ll lean towards 0.004” per inch of bore for the top ring. Older conventional thinking has the second ring end gaps at 0.003” per inch of bore but this thought process has changed in the last twenty years to having the same end gaps as the top ring and in some instances, more. If there is an expansion groove or a large distance between the top and second ring grooves in the piston, then the second ring gaps being larger than the top ring gaps is not as critical unless it is a high performance application. In those high performance instances, you’ll want a larger second ring end gap to prevent any unseating of the top compression ring in the event of a pressure build up between the rings. If the top and second ring grooves are close together and/or there is a very small or no expansion groove present, then it is typically advantageous to have a ‘generous’ second ring end gap regardless of the end use to prevent the aforementioned pressure build ups between the top two rings unseating and thus breaking the ring seal to the cylinder.
Where metric rings are being used and these being much narrower in width than the stock 5/64” or 3/32” width rings, then the top ring gap for a street engine is typically 0.0045” per inch of bore. The thinner rings typically have a higher expansion rate than the thicker rings. Second ring end gaps are the same or opened up to 0.005” per inch of bore depending upon the application.