Oiling system mods

The sleeved lifter bores fix most of the oiling deficiencies in a 351C. The verticle hole in each main bearing web only blocks off oil to the cam bearing directly above; your rebuilder may have decided to not do them for whatever reason. Those drillings typically are plugged with varnish just below the cam bearing anyway, and changing cam bearings in a Cleveland is much more difficult than on most other engines. #5 main has a 3-way oil drilling- the verticle one is for the rear cam bearing, the rt drilling is for the pssenger lifter bores that you have fixed by sleeving. So your rebuilder didn't go all the way with the restrictors, but the possible gains are pretty small.

Incidently, if you want to get into this subject a little deeper, I wrote a 4-page in-depth article in the Tech section of the Dec 2002 POCA Newsletter, with illustrations, photos and a 'map' of how oil flows around and around in the 351-C engine block. Frightening that Ford with thousands of engineers working for them, came up with this design for their premier performance engine of the '70s...

Beyond the sleeves on one side, the other bank is still vulnerable to roller cam wheels being lifted into the remaining big transfer holes, and a high performance 351C really needs an Aviaid or equivalent baffled/trap-doored oil pan with its larger pickup, plus a Milodon or SVO hardened oil pump driveshaft, and the roll pin in the distributor drive gear beefed up. If the pump don't spin, or the oil runs away from the pump pickup its all for nothing.