The center gallery has drilled passages that go to the cam bearings, and the oil follows a counterbore around the back of the cam bearings down to the mains. From the mains, drilled passages in the crankshaft lube the rods. I've seen individual rod journals lose lube because of a clogged passage between the cam and the main bearing. That causes one spun main, and failure of the two rod journals that main bearing supplies. The worst "OOPS" I saw involved a race engine crankshaft with a mud wasp nest in one crank passageway. The guy had all the pieces of his backup engine in the corner of his shop, covered up with a tarp. He blew up his engine one night, went back to the shop and assembled the spare in a hurry, and didn't check the oil galleries. The engine had good oil pressure on startup, so he ran it up to 2K RPM to break in the cam. Spun rod bearing! Scratch one $6K race engine!
Jerry
