The ugly truth about OE Timing Gears

[Mike P]

Most if not all of the American made V8 in the 60's thru the 80's used a timing chain set with a nylon cam gear. Usually at about 100,000 miles the gear would start to disintegrate.

If you were real lucky the engine would just die when the chain slipped and not bend any valves. In a lot of cases a new chain would be installed and the car would go down the road again.

Worse case however would be the brittle nylon chunks of gear (along with pieces of valve seals which also seem to give up the ghost at about 100K) would plug the oil pickup screen and drop oil pressure. An even worse scenario would be a piece of the gear getting into the oil pump (particularly on Fords which had a spring steel that would open allowing all kinds of crap into the pump) seizing the oil pump bit allowing the engine to still run.

This is a picture of part of the crap that came out of the oil pickup on the 500 Caddy. The engine had had a new timing chain at some point prior to it being parked, but no one had bothered to pull the pan and remove the crap that was plugging the majority of the pickup.

This is the main reason that when I do come across an original low mileage engine from that era I usually plan on pulling the timing cover and pan to see what’s under there.