[thepontiacman]

Most here know this is a V8 Pontiac timing set. Original fiber tooth cam gear. Just pulled out of a 87,000 mile 400. Most of these didn't last past 90,000 miles before loosing teeth.

[poncho-mike]

Believe it or not, I had a 1978 Suburban 3/4 ton 454 that had a nylon tooth timing chain gear set I got 180K miles out of it.

Around 1990, I bought a 1978 Suburban 3/4 ton from an older man who used it to tow a camper. It had 60K original miles at the time. I drove it for at least 15 years, one day I went out and it didn't crank. I could tell by the way the engine turned over something wasn't right and I suspected a broken timing chain. I pulled the distributor cap and found the rotor button wasn't turning when the motor was turning over.

I was amazed when I tore into it that the engine had a nylon tooth timing chain gear set.

[72projectbird]

The 70 T/A had it.

The teeth were in the bottom of the pan. lol

[Fullsize455]

I pulled the original set out of my '71 455 when it finally slipped at 212k miles.. I've got it in a box somewhere, gonna hang it on my wall again when I move into my next shop.

I suspect the original is still in my 211k mile '70 455 I just picked up.. gonna find out over the winter some time when I tear it down!

[george kujanski]

Back in the late 60's I knew at least 6 Pontiacs from friends and family that had a failed timing gear at about 50K miles. Every time i heard of one i asked the mileage...about 50K each time....no kidding.

George

[dataway]

Back in the day when they often failed, the ones I pulled out almost always seemed like they might have been over heated a few times. Not so much a wear problem, as a problem with the nylon getting brittle from excessive heat. Or at least that was my gut feeling looking at them.

[77 Canamman]

This and cast rods were two Pontiac (GM) engineering faux pas. Planned obsolescence at its epitomy.

[SRR]

Nylon timing gear.

[SRR]

Originally Posted by 77 Canamman

This and cast rods were two Pontiac (GM) engineering faux pas. Planned obsolescence at its epitomy.

How many cars went to the junk yard prematurely just because of these type of things.

[74Grandville]

not a pontiac, but i'm going to do the timing set on my 79 F-350 this week just for this reason. It has 78K on the orginal 400. when i replaced the fuel pump a couple weeks ago i reached in to feel the play in the chain and it was flopping around. i'm surpised it hasn't jumped a tooth.

From what i have read it reduces the harmonics to create more stable timing. they probably did not design them to last 40+ yrs.... lol

[geeteeohguy]

About 2 years ago, helping a forum member reseal the 61,000 mile original engine in his '69 GTO. Cleanest 400 I've ever seen the inside of. Lowest mileage, too. The teeth were all hard, cracked, and brittle, but hadn't failed yet. We swapped the set out with steel gears. Car runs like a new car....it practically is!

[mgarblik]

When I was 18, I bought a 66 4-door Ventura from my next door neighbor. His driveway was 30 ft. from my parents. I started it up, backed it out of the driveway to the street, put it in drive, gave it about 15% throttle and pop. Dead on the road. Pushed it in my driveway and took it apart. Plastic teeth in the oil pan and a chewed-up aluminum sprocket. Fixed it with a Cloyes set and drove it another 130,000 miles. The ONLY time it ever let me down.

[455Grandville]

Originally Posted by 74Grandville

not a pontiac, but i'm going to do the timing set on my 79 F-350 this week just for this reason. It has 78K on the orginal 400. when i replaced the fuel pump a couple weeks ago i reached in to feel the play in the chain and it was flopping around. i'm surpised it hasn't jumped a tooth.

From what i have read it reduces the harmonics to create more stable timing. they probably did not design them to last 40+ yrs.... lol

I’d drop the pan and do the rod bearings while you’re at it; 400 Fords are hard on their bearings.

[njsteve]

Back in the day, up here in the Northeast, instead of marking the passing of the Fall to Winter season with the Winter Solstice we would determine the true start of winter by the number of Pontiac timing gears that would self-destruct. That day marked the first true day of Winter.

[GT182]

My 79 Formula came with the nylon timing gear set. It lasted a little over 40,000 miles and had to be changed out... to an all steel set. I changed it out in my dirt driveway laying on a cardboard creeper in late January on a Sunday, up on the Canadian border in Northern NY.... Rouses Point, NY to be exact. LOL Boy was it cold.

[Fullsize455]

Interesting thread. I have run into a lot of nylon cam gears on a variety of FoMoCo and GM engines over the years with far more than some of the mileages listed here. Interesting that so many seemed to fail so early, yet some seem to make it 200k+ miles.

The original nylon set in my '72 Continental 460 was still quite serviceable at around 140k when I replaced it in 2008 or thereabouts. I mean, it was showing cracks and obvious wear, but it wasn't shedding teeth or otherwise self-destructing yet. Now, the chain in my '71 455 shed all of its teeth when it slipped at 212k. I had a blast pulling the engine and tearing it down to clean out all of the little bits of gear teeth strewn throughout the motor.

Of course it should be said, the easiest way to check for a loose chain without digging into the motor at all is to hook up a timing light and watch the marks on the balancer. With a fresh tight chain, the mark will be rock solid steady. With an old loose chain, the mark will be wavering around even at a smooth idle. A badly worn loose distributor can potentially affect your timing marks when checking with a light as well, but a rock solid mark means everything is tight and in good order.

[mgarblik]

Originally Posted by Fullsize455

Interesting thread. I have run into a lot of nylon cam gears on a variety of FoMoCo and GM engines over the years with far more than some of the mileages listed here. Interesting that so many seemed to fail so early, yet some seem to make it 200k+ miles.

The original nylon set in my '72 Continental 460 was still quite serviceable at around 140k when I replaced it in 2008 or thereabouts. I mean, it was showing cracks and obvious wear, but it wasn't shedding teeth or otherwise self-destructing yet. Now, the chain in my '71 455 shed all of its teeth when it slipped at 212k. I had a blast pulling the engine and tearing it down to clean out all of the little bits of gear teeth strewn throughout the motor.

Of course it should be said, the easiest way to check for a loose chain without digging into the motor at all is to hook up a timing light and watch the marks on the balancer. With a fresh tight chain, the mark will be rock solid steady. With an old loose chain, the mark will be wavering around even at a smooth idle. A badly worn loose distributor can potentially affect your timing marks when checking with a light as well, but a rock solid mark means everything is tight and in good order.

Much as I hate to admit it, Pontiac engines seemed to have a much higher failure rate on the plastic cam gear than any other brand of engine I can remember working on. Lots of Fords, Buick, Olds, Chevy big and small block all used them. They all wear out eventually, faster with poor maintenance. But I honestly can't remember ever seeing a Pontiac go past 120K-130K maximum without shelling the plastic off the cam gear. I have taken apart many other brands with higher mileage and deep wear in the plastic, but the teeth were still in tact. The "official" reason for using them was the quieter operation, but I can't ever remember hearing an all steel set make noise. Not a great design for longest life.

[carcrazy]

Originally Posted by george kujanski

Back in the late 60's I knew at least 6 Pontiacs from friends and family that had a failed timing gear at about 50K miles. Every time i heard of one i asked the mileage...about 50K each time....no kidding.

George

That was my experience. Rarely lasted much longer!

[Heybuck]

Don't remind me about fibre timing gears.

Not timing gears but way back maybe 38 years ago, I was driving a rental car (for business) in England. A Hillman Hunter. DREADFUL car. 4 cylinders of nothing...

I was about on my last day travelling and heading back to London when the fire just went out. Coasted to a stop and could not see any reason. NO mobile phones in those days but not too long later a sort of sweeper van pulled up. They used them (maybe still do??) on the motorways to clear broken down cars. He hooked it up and towed it to a service centre which was nothing more than a fuel station come junk food stop. From his point of view, the car was off the motorway and the rest was up to me.

Phoned the rental car company. HOPELESS. Can't do anything till tomorrow.... I had to hoof it over to a cheap rooming house for the night and about 11 hours later they sent a mechanic along who must have known in advance what the likely problem would be. He pulled out the distributor, Fibre gear driving the distributor. Hammered on a new one and off it went.

What a heap of junk...

Ian

[Formulabruce]

Can tell you this, MOST made it WELL past their warranty period.