I blew the engine in my mom's '68 Lemans. I was drag racing an '85 Olds 442 for a couple miles.

Nylon Timing Gear
 

My brother's '70 GP made it to 90K before it jumped time and left him stranded. He bought the car in the early 80's with 29K miles.

The dreaded nylon camshaft gear.

In regard to the Pontiac GTO, plus other GM models and/or manufacturers.

1964 and 1965 used a Hardened Alloy Iron gear.
1966 through 1972 used that “stupid idea” Aluminum Alloy with Nylon Covered teeth.

Replaced dozens of those in all GM engines but Cadillac. Might have had it, but I don't recall ever working on one.
We always quoted the customer a price to replace the gear set and another to remove the pan and clean all the crap out, that was restricting the suction screen on the oil intake tube.
99% just paid for the gear set change and then sold the car. Some came back later for LOF's in Ford's and Chrysler's. They said they didn't want to pay for that again. I reminded them that it was noted on their bill that the replacement set was steel and would outlast the rest of the engine.

I think we're supposed to do that... makes it easier to shame the kid into helping fix it. Cale learned how to swap the transmission in our '01 Trans-Am this summer because it broke while he was driving it.

Me: "So, how hard were you beating on it when it broke?"
Cale: "Not any harder than Mom does."

Did that too. If it sounded faster, it was! LOL

I just laughed my azz off... for those that don't know, Jenna drag races that car at times and I can imagine Cale was right ...:biggthumpup:
Derek is a VERY lucky man to have a wife that supports and participates in his racing and collecting addictions.

I believe the Aluminum/Nylon gear was designed to reduce noise and harmonics in the valvetrain, but heat and contamination damaged the nylon very quickly, turning it brittle and hard. May have been a cost saving as well as there was little machining done to the gear, just the cam bolt area, the rest was molded. One left me stranded in my 69 Plymouth Satellite with a 318 at around 100K. At least the 340 came with a double roller timing chain with cast iron gear from the factory.