I'm going to put a new timing chain in my sbc 350. In looking at all the timing chain set-ups out there, I noticed some of the cam gears are solid (no holes around the circle) and some have 6 or 8 holes drilled in them. Where does the oil come from that lubes the timing gears and chain. Is it pumped out from behind the cam gear or slings up from an oil hole in the crank. If it's pumped from behind the cam gear wouldn't it be better to get a timing chain with holes in the cam gear so the oil would run down the front side and lube the chain and crank sprocket. Just wondering. I know alot about engines just not how all the oil is pumped around to all the places. Thanks: