Boom wrote:
what does the chart mean? ABCD is that measured in four spots? checking for out of roundness or something?
Yup, you got it Doug. I check everything across 4 diameters that are 45 degrees apart. Then I compare the averages, mins, and maxes to get average, minimum, and maximum oil clearances between journals and their respective bearings. That way if there are any tight spots you know about them and can do what's necessary to remedy the situation. Sometimes bearings can be out of round, so can journals for that matter, or there can be a problem with the bearing saddle...
I do that for main bearings, rod bearings, cam bearings, lifters, and the oil pump, and I also blueprint the distributor drive pinion and the oil plungers. On the top end I like to hand-lap valves even on new heads. Parts can be so variable these days I don't trust ANYTHING with out measuring it. High end motors are too expensive to risk having a failure because of a bad bearing that could have been replaced before the engine went together.