Nylon cam gear years

[ASPEC]

Good Morning,
Does anybody know in what years and in what GVW that GM used the nylon cam gear in the mark IV 454? Searching yielded no definate answer.
Thanks in advance for your help.

 

[edgephoto]

I just replaced the timing set on my 1987 GMC. I have owned it since 1988. It had nylon teeth on the cam gear.

 

[bucket]

My '91 454 has the original nylon cam sprocket still.

 

[legopnuematic]

Not definitive, but this is from the 1973 truck service manual, depicting a big block with nylon cam gear:

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[Goldie Driver]

My '91 454 has the original nylon cam sprocket still.

I thought that was a 70s only dumb idea.

I was obviously overestimating their ability to correct previous errors...

 

[Ricko1966]

I thought that was a 70s only dumb idea.

I was obviously overestimating their ability to correct previous errors...

It wasn't a dumb idea,and most of the cars went thier whole life without a failure,the transmissions gave up,the bodies rusted away,and the rings gave up way more often than timing gear failures. But the dealers weren't getting noise complaints. Smokey Yunick and Cliff Ruggles prefer them for racing applications. Now we don't say Honda,Toyota,Mazda,VW everyone is stupid when timing belt fails at 10 years 120,000 but was supposed to be changed at 5 years 80,000 we look at that as owner neglect. A timing set is a wear item also. Supposedly the O.G. Gm Morse chain and nylon sprocket is more efficient and controls timing better than a double roller. Just change it at 100,000.

 

[ASPEC]

Not definitive, but this is from the 1973 truck service manual, depicting a big block with nylon cam gear:

Yup, the 1974 shows the same photo...

It wasn't a dumb idea,and most of the cars went thier whole life without a failure,the transmissions gave up,the bodies rusted away,and the rings gave up way more often than timing gear failures. But the dealers weren't getting noise complaints. Smokey Yunick and Cliff Ruggles prefer them for racing applications. Now we don't say Honda,Toyota,Mazda,VW everyone is stupid when timing belt fails at 10 years 120,000 but was supposed to be changed at 5 years 80,000 we look at that as owner neglect. A timing set is a wear item also. Supposedly the O.G. Gm Morse chain and nylon sprocket is more efficient and controls timing better than a double roller. Just change it at 100,000.

Agreed. Was just hoping I wouldn't have to go in there. Truck has a numbers matching engine, frame, trans, dif, and it doesn't look like the heads or front tin have ever been off. Heck the water pump looks original with gm cast part numbers and all...
Can't risk damaging a 50 year old survivor big block so in we go.

Thanks everone.