on my LA engine the passenger side top cam retainer bolt passes through to the valley. That is the one that should have a hole in the bolt. I think the idea is that the oil drips out from that hole and runs onto the tab and onto the chain. I know I forgot to put a drilled bolt in there and ran no oil slinger and my chain was smoked in 5000 miles. I just recently put it back together and corrected those issues.