Plastic Timing Gears?
 

I know from experience with my '78 K25 and '79 G15 that the plastic timing gears can be counted on to fail at right around 130K miles. If I knew then what I know now, the bent valves and bent pushrods could have been avoided by replacing the timing gears sooner. My neighbor has a '94 C10 that is nearing the magic number. Does the' 94 350 engine also have the plastic gears?

While I can not say with 100% assurance...I am pretty sure the answer is no.

does the 250 6cyl have plastic gears?

How about a 92 350 in a truck?

They went to metal gears in the V8's in the later engines as far as I've ever seen. The latest I've seen with the phenolic gear was an 85 if I remember correctly.

Beard, yes, the 250 should have 1 aluminum gear according to Santucci's 6 cylinder manual, but no plastic gears.

Sorry to say, I've not heard of that manual.

Thought maybe I was having problems with mine. Seems to be a good 6 buy no power range.

Thanks

Chevrolet Inline Six-Cylinder power manual by Leo Santucci.

Buy one.

No joke.

Every 6 cylinder guy simply must have this book. It's under 20 bucks new. Has factory engineering drawings showing sizes of bolt holes, casting numbers, build up guidelines, everything.

Correct me if I'm wrong, but the inline 6's have plastic counter rotating gears. No chain.

The reason they have palstic or resin gears is to keep the noise down. I've had many late 60's early 70's engines have chains jump, or worse, plastic pieces come off the gears, and jam up the oil pump. fun!. you can really hear those metal gears whirring. Dunno 'bout later vehicles. kinda stopped caring about '82-up.

Sounds like I need one of those to go with the 250ci I6 in our 18' tri-hull!

Negative

They have a steel crank gear that meshes directly with an aluminum cam gear. No chain, just gear to gear.

I just disassembled my K10's 350. Looks to be never rebuilt. The plastic teeth on the cam sprocket were all there, just not altogether.:lol:

One could see about 30 stress fractures; half open cracks, half cracks that hadn't opened yet. The timing chain had mucho slop. At least an inch movement installed. I'm surprised the plastic held out as long as it did. I'd guess that the loose chain rode easy on the teeth so it didn't break. Just conjecture, really. :D

My son's IL-6 had plastic gears. It was in a '74 Chevy. The gear went out on his and had to replace both of them.

Just did a 91 suburban rebuild . It was a plastic gear unit. definatly stock. 2 missing teeth from the can sprocket so I had to pull the oil pan Hmm ... well I found 1 of them anyway. guess the other came out in an oil change or something alson the way.

6-cyl. engines destined for car use were made with plastic timing gears, but not the same type of plastic used in V8's. Truck 6's had metal gears.