Quote:
Originally Posted by mgarblik
I have a feeling I will get trashed for this post, but my experience over many years is the ring end gap is not critical to final engine performance within reason as long as their is enough gap for the application. Let me explain. I have never seen an engine fail from too much end gap. Too little, absolutely. Catastrophic engine damage if the rings butt together. Too much side clearance, same catastrophic damage as the ring lands break. As far as end gap, I remember some extensive gap testing Warren Johnson did on Pro Stock engines. They tried all kinds of end gaps on top and second rings. They had top end gaps as wide as .060 and no loss of power on the dyno. Actually found small power increases as they widened the gaps into the .035-.040 range, then little to no change up to .060. When Joe Mondello was alive he agreed with these findings in his own experiments.
So what does matter? To get accurate end gap readings, the ring must be absolutely square in the bore as mentioned. If you file the end gaps to gain more clearance, they must be filed or ground straight and all edges dressed with a diamond file or tiny stone. This goes for new rings that have not had the gaps altered. If you leave sharp edges, the rings act like little chisels in the bore. Like many have mentioned, I too like .003-.005 more end gap on the second ring. Oil rails are worth a look as mentioned, usually do not require opening the gap. If I have a target gap for example of .022" and I end up + .002-.003, I would install and never worry about it based on the research I have read. Back in the old days, I would have replaced the rings.
Dataway, I think it is great the way you are experimenting and learning all the details of your engine. I used to do these kinds of things all the time and then be puzzled for months or years about my results in the days before the internet. Good luck with your engine.
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I will "amen" all of that.
During my stint at Valvoline, I had to do calculations to see how much end gap was necessary to actually cause blow-by. The engine lab had dozens of engines running at all times, in order to recreate different running situations, including high-mileage engines. You could get into some DEEP ring end gaps without causing issues.