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.

 

[Goldie Driver]

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.

To each, their own. I am not a fan of timing belts either as I see that as a planned obsolescence. Timing chains are typically a life of the engine item if the engine is maintained and the gear & chain are metal in my experience. Most of the nylon coated ones I saw failed around 70K.

 

[fast 99]

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.

Some of the 90's and up GM V-8's came with a single roller chain. Replaced several high millage motors and frankly the chain was tight enough to reinstall. Wonder if this was a replacement for plastic?

Back in the late 70'S and early 80's I replaced a ton of failed Pontiac plastic timing chains. Most vehicles were likely near the end of their life. Unsure why we saw more failed Pontiacs than other brands but we did.

 

[Ricko1966]

Some of the 90's and up GM V-8's came with a single roller chain. Replaced several high millage motors and frankly the chain was tight enough to reinstall. Wonder if this was a replacement for plastic?

Back in the late 70'S and early 80's I replaced a ton of failed Pontiac plastic timing chains. Most vehicles were likely near the end of their life. Unsure why we saw more failed Pontiacs than other brands but we did.

That's kinda strange with the Pontiac failures,maybe a run of bad gears certain years. Everyone started running nylon gears on Damm near everything early 60s . Ford,AMC,Chrysler,all the GM lines, they were still running them in the Grand Nationals and Corvettes through 91. Sorry @fast99 now I've gotten off track,and wish I hadn't quoted you. Anyway as many millions and millions of cars had these gears sure some are going to fail. I've heard of way more spun bearings,rods through blocks,Damm near every kind of failure other than cam gears. Sure I've seen a couple,but back too the original point,kinda strange that you saw such a high incidence on Pontiacs,wonder if they had a run of bad gears at some point. I still think 90 percent or more of cars with nylon gears were junked or got engine rebuilds with the original timing gears still in them and functioning. Remember life span of a car back then was 10 years 100,000 miles