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.

[pat mccarthy]

yep RTV is the new nylon teeth in the oil pump pickup we pull a pan on warranty at the boat yard and someone put the old oil pan set IN THE PAN and put it back on with a new pan set thank god there were no paper towels in the pan .... i think the guy that did that job just wipe his hands on his underwear

[Itoldyouso]

Yep, I had a 63 Pontiac 389 that one of the teeth on the plastic timing gear came off and went into the oil pan. Coincidentally, the pickup had fallen off the pump so it was a straight shot for the piece of plastic to get sucked into the open hole, jam up the pump gears, and shear the pump drive. When I rebuilt it I made sure I brazed the pickup on the pump and put a steel timing set in place of the plastic type.

One of Detroits "better" ideas that wasn't.

Don