I had 5-30 in it on my original startup with the used lifters, but ditched that for the 10-30 before trying anything else. I was thinking of trying something else, but due to the fact that almost all of the other lifters are running perfectly, I figured this is an issue with the oiling system rather than the oil. Any idea if I can pressurize any part of the system to try to clear it out? This is a brand new freshly rebuilt engine, so I can't imagine what could be clogging it up.