When did GM stop using the nylon coated gears on their SBC Timing Chain

[texas-topper]

Hi All,

Quick question,....If, and when did GM stop using the nylon toothed sprockets on their timing chain setup on small block chevy engines?

Back in 1979 I had a 1972 Chevy truck with a sbc 350. I found out the hard way it had the nylon teeth on a steel sprocket setup for the timing chain. Needless to say I learned how to replace the timing chain way back then.


I now have a fairly low milage (54,000) 1978 Chevy Big 10 with a 350 and I am concerned it could have the same nylon gears as the '72 chevy had. Let me know when and if GM ever stopped using tthe nylon tooted gears.

Thanks for the help,

Ken

[Walts_restoration]

Having a big ten, you have the non-emissions 350 i assume, non egr, no cat, basicly the same motor the 3/4s and up used, in otherwords, you have my blue trucks little brother. I can gurrantee you that the motor in your truck wont crap out as long as its maintained right. Trsut me, occasionly i have to blow a honda or two off the raod when im driving the truck, probally becuase i ran the camaro out of gas. For a stock motor it is indestructable.

I dont know wether or not it has the nylon gears, but anyways, glad to see another Big ten on here, representing the gas guzzling trucks of the 70s

[texas-topper]

Yep,....this truck has no emissions on it,......it's great!!. Like you said, it doesn't get great gas milage but it's not too bad.

I have only had the truck for about three to four weeks. The truck has not been abused but it has been somewhat neglected the last several years. The son of the original owner inherited it about seven years ago. He drove it,...but not often. It looks like the dad kept it parked under covered parking, and I suspect the sun kept it under some trees.

Anyway I am in the process of installing a new radiator and water pump (for insurance and peace of mind) and while I am have it this openede up I was eying the timing cover and wondering what lies underneath?

[454HO]

Originally Posted by texas-topper

Anyway I am in the process of installing a new radiator and water pump (for insurance and peace of mind) and while I am have it this openede up I was eying the timing cover and wondering what lies underneath?

So why not just get a OEM replacement chain and slap it on there? Then you know for sure it's good!!

[dswancutt]

I have a 78 big 10, it had the nylon timing gear.

[Walts_restoration]

Id say if your gonna replace it, go for a double chain true roller, that way its there and dependable.

[texas-topper]

Well the cam sprocket on my '78 Big 10 was indeed nylon just like dswancutt's said his was.

Originally Posted by dswancutt
I have a 78 big 10, it had the nylon timing gear.

The old timing chain and spockets still looked good but there was no way I was going to trust a twenty-nine year old nylon, overmolded sprocket,...so the old stuff is out and a new Cloyes double roller timing chain set is installed and buttoned up.

I sure remember the job of changing out a timing chain being easier back in 1980 when I replaced the timing chain on the '72 Chevy I had then,..... of cource I was seventeen and much more flexable and limber (code words for I am too fat now)......

Thanks to all who replied for your help and suggestions.

[gchemist]

The nylon gears destroyed the 305 in my truck.

[dswancutt]

I think you did the right thing by replacing the timing chain, especially if you had it tore down anyway. I was a lot luckier than gchemist when the timing gear failed on my 305 that I had in my 78 k-10. Was going back to see my folks, had done a long highway run, drove a little ways in town, pulled up to a stop sign and she died. No damage to the engine. Ran way better after that, well as good as an worn out 305 can run. Don't need to worry about it now. Rebuilt the original 400 sbc, had it built with 350 rods for a little longer stroke. Just need to finish getting it together and slap it in the old beast.

[jeffspower]

IIRC the '87 FI SBC engines were the first to go steel. The 301 Pontiac was the first GM V8 to use a steel cam sprocket- I think that was in '77.

I've seen some of the old chevys nylon jobbies make it 200,000 miles, some as little as 75,000. And the old saying "a stock small block won't bend valves when the chain goes" isn't always true.

Put one in while you are so close.

[Pyrotechnic]

If you can, also change the oil pump drive shaft to one that has a metal bushing rather than the stock nylon. That and the timing chain and you have a motor that will give you lots of useful miles. Spring for a good timing chain like a cloyes true roller. I pulled an all steel stock replacement chain off my motor that didn't have a ton of miles on it but it was streched like it had 200,000 on it.