2 Factory timing sets do a good job, however, there’s more friction and they don’t last as long as rollers. The most troubling issue is OEM nylon-coated aluminum timing sprockets used for noise reduction during the 1960s, 1970s, and 1980s. These coated gears were quiet, but they didn’t wear well. When they failed, they caused valve to piston contact and bent valves. Worse yet, these failures put a lot of nylon and aluminum trash in the oil.