Nylon Timing Gear & chain replacement

[Dan B.]

I just wanted to post my own experience with the 67 and up GM Nylon / plastic timing gear. I recently had my intake removed to address an oil leak and was able to inspect the Nylon cam gear from the backside. It appeared in good condition as far as it was complete with no visible cracks or missing pieces. However, I had what I believed to be an unacceptable amount of play in the old chain so I decided to tear it down and replace the gears and chain. While removing, the Cam gear it broke in my hands (and the chain did have a lot of play). Boy was I GLAD I made the call to R&R. One thing that should not be overlooked is the long term heating / cooling effects on the plastic in so far as it becoming brittle. I just wanted to pass this along to anyone who may still have one of these in their engine. You might want to think about being proactive about this repair. Special thanks to Joe Lucia & Duke for their prior posts on the subject which inspired me to make this a priority job! Dan

[Mark E.]

Re: Nylon Timing Gear & chain replacement

Thanks for the heads up, Dan.

What type of timing set are you using as a replacement?

[Dan B.]

Re: Nylon Timing Gear & chain replacement

Mark, I used the Cloyes double roller Chain. It's a nice beefy chain and it fits very snug compared to the old sloppy one. The parts are quite reasonably priced, the job is all labor but not too bad. It's gonna take me longer to clean and paint and detail all the surrounding parts than the actual repair

[Loren L.]

Re: Nylon Timing Gear & chain replacement

I don't know if it's still true, but you used to be able to get the Chevy parts guy to look in the truck parts book for GM's version of the double roller chain.

[Gary R.]

Re: Nylon Timing Gear & chain replacement

Hi Dan
I torn down old 350's in the past and found white nylon chips in the timing cover and the teeth sharp. When I bought a new GM crate 350 back in '82 I torn it down and replaced the new nylon timing set in it.

On the Cloyes set, they used to be the best but there might be two versions now and the lower priced sets are imported I believe and sloppy. The better usa ones are tighter. I haven't bought a set a few years now so I don't if they changed anymore. The last one was to replace a new Steel v tooth set that was made by Comp and had a lot of play in it.

[Dan B.]

Re: Nylon Timing Gear & chain replacement

Hi Dan
I torn down old 350's in the past and found white nylon chips in the timing cover and the teeth sharp. When I bought a new GM crate 350 back in '82 I torn it down and replaced the new nylon timing set in it.

On the Cloyes set, they used to be the best but there might be two versions now and the lower priced sets are imported I believe and sloppy. The better usa ones are tighter. I haven't bought a set a few years now so I don't if they changed anymore. The last one was to replace a new Steel v tooth set that was made by Comp and had a lot of play in it.

Hey Gary,
The set I got is USA made and it is super tight. Actually, I had a bit of a time getting it on (it is a light press fit). Zero play installed now, and so much stronger than original and light years ahead of what I removed. Kind of like the way you rebuild the rears, much better than original :-) so I am a happy camper. I did elect to use the die grinder to smooth the 12 O'clock position as it was too close for my liking. No big deal, just a few extra minutes for piece of mind on the install. Cheers!!!!

[Steven B.]

Re: Nylon Timing Gear & chain replacement

Cloyes Tru Roller chain sets have always been a good choice. I don't know about now, but in the past the chain was manufactured by Reynolds of England and was guaranteed not to stretch. They also have multiple key-ways. At the time (80's) it was one of the only double true roller chains around. I believe that they may have been OEM suppliers at some point. I could be wrong about that.
Steve

[Joe L.]

Re: Nylon Timing Gear & chain replacement

Cloyes Tru Roller chain sets have always been a good choice. I don't know about now, but in the past the chain was manufactured by Reynolds of England and was guaranteed not to stretch. They also have multiple key-ways. At the time (80's) it was one of the only double true roller chains around. I believe that they may have been OEM suppliers at some point. I could be wrong about that.
Steve

Steve------

The Cloyes Tru Roller is the ONLY timing set I will use. Period. For a Mark IV big block it's Cloyes #9-3110.

[Joe L.]

Re: Nylon Timing Gear & chain replacement

I don't know if it's still true, but you used to be able to get the Chevy parts guy to look in the truck parts book for GM's version of the double roller chain.

Loren-------


No longer available. Plus, when they were available, they were only available as individual pieces, not a complete set. The cost of the individual pieces was more than the cost of a Cloyes Tru Roller, which is far superior. The small block Chevrolet truck roller was available as a complete set. Still, nowhere near as good as a Cloyes Tru Roller.

If someone with a 1966-69 L-36/L-68, 1970-72 LS-5, or 73-74 LS-4 wants to use a stock, original timing set, unwise as that might be, the parts are still available:

chain: GM #14103224

crankshaft sprocket: GM #3902426

camshaft sprocket (nylon): GM #330814

[R N.]

Re: Nylon Timing Gear & chain replacement

Steve------

The Cloyes Tru Roller is the ONLY timing set I will use. Period. For a Mark IV big block it's Cloyes #9-3110.

Joe, could I trouble you for the p/n of the Cloyes Tru Roller for my 67 L79 please & thanks?

[Leif A.]

Re: Nylon Timing Gear & chain replacement

Cloyes part#9-3100 is your part.

[Dan B.]

Re: Nylon Timing Gear & chain replacement

Here is a picture of the broken gear. Luckily this happened on removal so I was able to retrieve the little pieces before they got into the motor.






New Cloyes chain installed

[Joe L.]

Re: Nylon Timing Gear & chain replacement

Here is a picture of the broken gear. Luckily this happened on removal so I was able to retrieve the little pieces before they got into the motor.






New Cloyes chain installed

Dan-------

The problem with the nylon sprocket is VERY common on both small blocks and big blocks. ALL 1965-74 Corvette big blocks were originally equipped with the nylon-toothed camshaft sprocket. ALL 1966-82 Corvette small blocks were also originally equipped with a nylon-toothed camshaft sprocket.

[Duke W.]

Re: Nylon Timing Gear & chain replacement

You can't go wrong with either a Cloyes/NAPA silent chain (C-3001K/203001) - the second design which is slightly narrower than the early silent chain - or the truck roller chain (Cloyes C-3023K/NAPA 103023). The Cloyes Web site says sprockets are steel, but I believe that the cam sprockets are cast iron, which is fine. Cast iron is very tough and has excellent wear characteristics. The steel crank sprocket is hardened steel for both strength and good wear characteristics, but given that the cam sprocket has double the number of teeth, unit loading is half the crank sprocket, so steel offers no advantage and would cost more.

They are both manufactured by Cloyes, but NAPA sells them under their own brand too, so buy on price (20-25 bucks for the sets) and convenience.

The truck roller chain can also be purchased with three indexing keyways on the crank sprocket to install the cam at as-manufactured indexing or advanced or retarded four degreesn - C-3023X/103023X.

Cloyes' "Tru-Roller" is just marketing BS. A roller chain is a roller chain - the roller engages the sprocket and rolls around the pin - just like a motorcycle chain.

The so-called "Tru-roller" has larger rollers - .250" versus .200" for the OE replacement truck chain set. The larger rollers will take greater shock loading, so if you regularly do 5000 rev clutch drops and power shifts, it may offer some durability benefit, but not too many do that, and it's common for the larger rollers to interfere with the timing chain cover, which requires rework to gain sufficient clearance.

It doesn't make sense to buy the aftermarket set which provides absolutely no benefit for normal road driving at over three times the cost of the OE replacement sets.

Duke

[Dan B.]

Re: Nylon Timing Gear & chain replacement

I decided to go with the Truck roller chain 3023K (pictured), perfect for what I wanted and more substantial. Big thanks again Joe And Duke for posting this info in the first place. Cheers!