I agree with Cab. I believe they figured the timing chain gets enough lube from the oil thrown off the # 1 bearing with a normal bearing in there. I honestly cant see the small chamfer on the edge of the bearing making much difference on how much oil is thrown out from the # 1 bearing. A Chamfer may just let the excess normal amount of oil thrown out spread a little more. But I also have never seen any bearing sets for 440 mains with a special bearing for # 1 and none have ever had timing chain abnormal wear. Ron