Some engines came from the factory with nylon coated timing gears to "quiet" down engine noise. It's been a very long time since I disassembled my 400, but I am thinking Pontiac did not use nylon timing gears on the V8's??? Others experts will chime in.
I didn't do the work when mine failed on my '68 400HO in 1974 so I can't say for sure. However, the mechanic that did the gear and chain repair then said the failure was because the nylon-coated gear got chewed up and the chain had jumped several teeth. .
