[Sirrotica]

This subject has been talked over before here, and as near as anyone can find, it looks like 1971 was the last year that a nylon gear was used, and it seems that there was a mid year change.

Parts books only list that the gear was still available through GM parts channels for a few years until the supply was depleted, not that it was still being used in the finished product.

Back during that time frame if you called a parts store, they would ask you if you wanted the nylon gear, or the steel one, as both were available from the aftermarket. I never opted for the nylon one.....LOL We already knew what the track record was for them.

I've seen them fail with as little as 25,000 miles, and if you got 60,000 out of one, you were really fortunate. Cars that got beat on (GTOs, Firebirds) seemed to expire first. The B body cars that got driven by more conservative drivers, lasted the longest, but the nylon still got brittle after many heat cycles, and turned to powder.

The only good thing from that debacle is, I would go to the wrecking yards, and sort through the core pile, and get perfectly good engines that were replaced because the timing gears broke. The geniuses that called themselves mechanics, couldn't troubleshoot the problem, and diagnosed the engine as bad.

Back in the 60s and 70s the GM timing set for the 194 slant 4 was the hot setup as the parts were hardened to combat the harmonics of the 4 cylinder engine. I bought one of those sets in the early 70s and still have it in the 428 engine that was in my 69 GP dirt car in my signature pics.