[Rich D]

What was the last year that a nylon timing gear was used in the 400. Thanks

[25stevem]

1974 it look like from my parts book.

[Stan R]

My 1971 GTO was a late model year production vehicle with the 400 (shipped in April of '71) and came from the factory with the steel timing gears. Early production vehicles still had the nylon tooth aluminum sprockets.

[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.

[hurryinhoosier62]

Originally Posted by 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.

Brad, both my ‘72 Catalina and my ‘72 GP had nylon timing gears from the factory. I was the first person to change both of them.

[Sirrotica]

Originally Posted by hurryinhoosier62

Brad, both my ‘72 Catalina and my ‘72 GP had nylon timing gears from the factory. I was the first person to change both of them.

Steve I'm just repeating what the conscientious was that 71 was the final year, from a previous discussion.

I know for sure that my 73 T/A, GTO, and Grand AM had steel gears. There is a post #3 that a 71 GTO owner had a steel gear in his car......

My 1971 GTO was a late model year production vehicle with the 400 (shipped in April of '71) and came from the factory with the steel timing gears. Early production vehicles still had the nylon tooth aluminum sprockets.

So did Pontiac build some with steel and some with aluminum until they ran out? Or the warranty got so high they only built regular car engines with the nylon, and the HIPO engines got steel? As I said, owning 3, 1973 examples that were low mileage when I purchased them, and I was the first person to disassemble the engines, none of them had nylon sets.

Every time this subject comes up, there is no definitive answer. No one has shown a factory memo, either in a service department bulletin, or a statement to dealers that they were suspending nylon timing sets at such and such a date, I guess the argument will carry on until there is proof that Pontiac made an official letter, or bulletin, stating when they officially suspended using the nylon timing sets. Maybe there was never a cutoff point where all nylon gears in all engines were stopped.

I had some 71 and 72 engines, but by the time I got them, the mileage was too high to have a nylon gear survive.

[maxpowerta]

Not Pontiac but Somewhat related as it's a GM engine, I just tore down a brand new never fired 72 Oldsmobile 455 marine crate motor and it has the Nylon gears in it.

[Half-Inch Stud]

Geez, i thought 68 was the last nylon timing gear. I changed it out in '80-'81.
Was sure the 69 GTOs has steel. ..?

[Sirrotica]

Originally Posted by Half-Inch Stud

Geez, i thought 68 was the last nylon timing gear. I changed it out in '80-'81.
Was sure the 69 GTOs has steel. ..?

I owned a 69 GTO, it was nylon, I was the first one inside of that engine.

Problem being is as I posted earlier, you could buy nylon gears for a Pontiac up into the mid 70s from parts stores, maybe even later than that. So during that time in the 70s I was making my living twisting wrenches, and when you called for a Pontiac timing set you would be offered, the nylon, or steel.

Olds and chevy used nylon gears later than Pontiac did, and their failure rates were much lower than Pontiac. I believe it was because chevy and olds had a much thicker nylon portion around the hub of the gear. Pontiac was molded much thinner around the hub of the gear than either olds or chevy. were. That thinner outer covering was much more failure prone.

I once owned a 91 cavalier Z24 with the 3.1 V6, that ran almost even at 200,000 miles before the nylon gear shredded, it bent valves so that was the end for that car. I think it was less than 100 miles over 200,000, so I guess that was as far as chevy designed it to go........

I paid $200 for it with 110,000 on it, and scrapped it for right around $400, so the car owed me nothing. 90,000 miles for free.

FWIW, I googled nylon gears in SBC, and it also wasn't definitive, but I could find examples that said in 1987 there were still nylon gears in 305s. Olds forums showed the same thing, no definitive year when there was a company wide date that no more nylon gears were used. So it wasn't a corporate wide cutoff date that GM said no more nylon timing gears.

I guess the debate will not ever be settled, but I know ford also used nylon gears in some of their V8 cars.......

I also owned a 88 Fiero with the 2.5 Iron Duke that made 110,000 miles before the fiber gear lost all the teeth off of it. No timing chain, just gear to gear, same part fits the inline 6 chevys back thru 1963. A non interference engine so I just replaced the gear and kept driving it, and sold it at 140,000 miles still running fine with a steel gear.

I'm done beating this horse, anyone else, feel free to keep it going....

[Stan R]

I've attached a specifications page from the 1971 Pontiac Service Manual which designates the material of the camshaft sprocket as aluminum with nylon covered teeth for early production vehicles and designates hardened cast iron for late production vehicles. However, this does not prove that the aluminum sprockets didn't find their way into engines of '72 and later models.

[Tom Vaught]

I was changing 1972 Pontiac Engines Nylon Timing Gears for anyone who wanted the update to steel in 1972 at my Uncle's dealership.
On my Uncle's dime.

I probably changed no more than 10 of the Nylon timing gears during 1972, but my Uncle said it was "Good Will" and his nephew worked cheap, lol. In some cases I had to use the special GM tool to raise the front of the engine high enough to get the oil pan off the engine with the engine still in the car.

No love for the Nylon Gear Engineer.

Tom V.

[mgarblik]

When I worked at the Pontiac Dealership in 1979-1981, we were still getting tow-ins of Pontiac engines with failed aluminum/plastic timing sets. I never paid any attention to the year's of the vehicles, other than remembering one 68 Bonneville with a 428 HO in a 4-door car. The repairs were always out of warranty by that time. The only way to do the job right was to remove the oil pan and clean it out. We would encourage the customer to do this and also replace the oil pump as a precaution. As I recall, about 1/2 of the customers would opt for the correct repair which would increase the bill about $150.00. That was allot extra in 1980. That would be an oil pan gasket set, new oil pump and added labor, about 3 hours. The others would get the pan flushed out through the drain plug hole with solvent or kerosene. A gunked-up engine would often have the pick-up packed with cam gear plastic. The pumps with the scoop shroud around the screen were often packed-up tight with teeth. More than one car was towed back in with the bearings all burned up within a few weeks/months of the "budget timing set repair". Dealership would make the customer sign the work order declining the proper, complete repair. That would never fly today. The customer would get a new free engine most likely.

[25stevem]

Can anyone who has taken apart a stock 1970 RA4 motor confirm that it too had a nylon gear?

[PunchT37]

Originally Posted by maxpowerta

Not Pontiac but Somewhat related as it's a GM engine, I just tore down a brand new never fired 72 Oldsmobile 455 marine crate motor and it has the Nylon gears in it.

Daddy had a `79 Delta 88 with Olds 350. Yep, nylon gears. Packed oil pump screen.

[track73]

I changed the nylon timing gear on my 67 Catalina 400 in 1973. It was pristine. Another Pontiac with the same mileage had one that all was chewed up,. That car was a 68 model.

[Region Warrior]

My 67 FB 400 4spd made it to 81 till 47k. Alot of street racing after bout in 79 at 42k

[Tom Vaught]

Mike, My uncle believed in "Do it right or send it up the road to the "other" Pontiac Dealer."

He did not want to lose long time customers so he had his nephew do the work.
I could do one repair a day and he always bought me a nice steak lunch on those days. Plus he had the Special Kent-Moore tools.

Tom V.

[sdbob]

I took the 350 out of my 70 F. Back in 79. Oil pressure light was on. It had steel gears. However the oil pump pickup was clogged with the melted plastic. I replaced pickup engine was fine after ckg bearings. Also had 71 Formula 400,wifes driver from same dealer. No light but I pulled pan and put new pump,cleaned pan. Engine ran for yrs actually sitting in garage complete.Just my experience.

[geeteeohguy]

Originally Posted by Tom Vaught

I was changing 1972 Pontiac Engines Nylon Timing Gears for anyone who wanted the update to steel in 1972 at my Uncle's dealership.
On my Uncle's dime.

I probably changed no more than 10 of the Nylon timing gears during 1972, but my Uncle said it was "Good Will" and his nephew worked cheap, lol. In some cases I had to use the special GM tool to raise the front of the engine high enough to get the oil pan off the engine with the engine still in the car.

No love for the Nylon Gear Engineer.

Tom V.

I have that special tool that bolts to the front of the engine. My old boss was a mechanic at a CA Pontiac dealership in 1970 and said I could have it if I knew what it was. I told him what it was (don't know how I knew) and he gave it to me. That said, I will never pull a Pontiac oil pan 'in-car'. I know better, and I had 42 years in the auto industry.

[mgarblik]

Originally Posted by Tom Vaught

Mike, My uncle believed in "Do it right or send it up the road to the "other" Pontiac Dealer."

He did not want to lose long time customers so he had his nephew do the work.
I could do one repair a day and he always bought me a nice steak lunch on those days. Plus he had the Special Kent-Moore tools.

Tom V.

I was fresh out or school and freshly unemployed having just been laid off by Hobart Corporation after they closed the Dayton research division. So I was the "college boy" at the dealership and got all the worst jobs nobody else wanted to do. All the water leaks and wind noise, all the oil leaks and transmission leaks. Theft recovery. Can't remember how many mid 70's Trans Am steering columns I replaced. I could have the oil pan off any A or B body Pontiac or second gen F body in just over an hour. Job complete in 3 hours with new oil pump. And I was fairly slow compared to the super flat rate guys. I kept my mouth shut and just did what I was told. My dealer either didn't have or lost the Kent Moore tool for holding the engine up. I had wood blocks I made at home for each body style that I put between the harmonic balancer and a high jack stand. 1st Generation F body were the most difficult of all to R+R in the car. I would lower the pan, unbolt the oil pump and let it fall in the pan. Then remove together. To put it back together, you had to turn the crankshaft to just the right position so the counterweights would clear the pan to wiggle it back in. They were tough.