I reassembled my pistons and put new rings in. After some trouble with leaky valves, I re-ground them, sealed them tight, and put the head back on. I was getting pretty good leakdown results (using an air compressor), somewhere between 86-92% retention (14-8% leak), which is below the 20% threshold. But then I remembered reading somewhere that lubing the cylinder sleeves provides a better simulation of the engine runtime and would also improve compression so I poured 3-4 drops of oil in each cylinder through the spark plug hole. I went to re-rest leakdown and this time it was leaking 30-40%. The only thing that changed, literally in a matter of 5 min, was that I added some oil.
Was this a wrong thing to do? Are the compression rings (the upper two) supposed to be dry of oil and now I lubed them and thereby compromised their seal? Does oil compromise the expansion of the compression rings, seizing them shut? I know the bottom 3 are supposed to be scraping the oil but they never reach the very top of the cylinder even in TDC, leaving the compression rings lubed. Does that explain why the leak suddenly increased.
