Nylon Timing Gear & chain replacement

[Joe L.]

Re: Nylon Timing Gear & chain replacement

The term "True-Roller" is marketing hype. It implies that there is some functional/operational difference between the Cloyes expensive aftermarket set compared to the OE replacement truck roller chain. There is not as I explained in post #14 where I also recommended inexpensive OE-replacement sets and gave part numbers. It's amazing how inexpensive these high quality, durable sets are considering the dozens of precisely machined parts that make them up, but they have been manufactured in high volume for decades, which brought down manufacturing cost to unbelievably low levels.

The only difference I can see between the two is the larger rollers in the aftermarket chain, (which can cause interference with the timing cover in some cases), and I doubt if there is any difference in material specs, heat treatment, or manufacturing tolerances.

I've known Chevy owners over the years whose engines went 150-250K miles without every being opened up with either the wide or narrow Morse Chain with cast iron cam sprockets or the truck roller chain. All are very durable.

Guys obsess way too much over this. (They should fret more about SB conn. rods and BB valve springs.) The only timing chain sets that were ever problematic are the those with nylon tooth cam sprockets, and they are no longer manufactured by any source that I know off, and even if they were one would be a fool to buy and install a nylon tooth cam sprocket timing set. NOS nylon cam sprocket sets are useful for display purposes only!

All the other configurations should last the life of the engine, but the truck roller chain is likely the most durable, and it's the one I recommend for most rebuilds, especially SHP engines. If one has a base engine with AC and other luxury options, like an auto trans, a quiet exhaust system and doesn't drive the car hard I might recommend the Morse chain with a cast iron cam sprocket because it is quieter, but I doubt if the difference can be discerned from the driver's seat. Vintage Corvettes have a good deal of NVH compared to most contemporary cars of the era, but most guys find vintage Corvette NVH pleasant and part of the car's charm, especially engine/exhaust sound, which will likely cover up any difference in noise between a Morse chain and roller chain.

There are guys who claim they can tell which OE mechanical lifter cam is installed by listening to the car idle with the hood open, which I dispute. So far no one that I am aware of has ever claimed they can tell the difference between a Morse and a roller chain.

Duke

Duke-------


Each of the 3 components of the Tru Roller timing sets are different and of higher quality than those used in the much lower cost roller timing sets which they also manufacture. For example, the timing sprocket is ductile cast iron, hardened, and precision balanced to 10,000 RPM. The crankshaft sprocket is machined from a billet of very high quality steel and hardened. The chain is an ultra high quality Renold chain that is guaranteed not to stretch. The roller links in this chain actually rotate whereas those in lower cost "roller" sets often do not rotate (that's where the name Tru Roller comes from). The components of the Tru Roller sets are individually hand-matched to ensure there is absolutely no "slop" in the chain when installed in a factory-spec, non-line-bored engine (versions of the Tru Roller are also available for line-bored engines).

One of the early symptoms of timing set wear/deterioration is the "jumping around timing mark" syndrome when using a timing light to set the engine timing. My original 1969 350 started evidencing this problem to some degree after about 10,000 miles and it got worse as time went on. However, I have a 350 that I installed a Tru Roller timing set in 100,000 miles ago. That engine had a rock solid timing mark right until the day I pulled it out of the car. Would an inexpensive, double roller timing set have done as well. Maybe, maybe not.

As far as nylon toothed timing sprockets go, they were still available up until at least several years ago but VERY hard to find. For some unknown reason, I wanted some and determined by calling Cloyes that they were all still available. But, I couldn't find any retailer that would order them for me. I finally had to get them directly from Cloyes but they had a stiff minimum order. I bit the bullet and ordered a bunch of them. I got the wide big block, wide small block, and narrow small block [none for sale]. I didn't need the narrow big block since I had several GM examples of those which are still available from GM to this very day.


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[Joe L.]

Re: Nylon Timing Gear & chain replacement

All-------


By the way, it's not just the cam sprocket nylon teeth that break on stock GM Morse-type timing sets. Note the attached photos of a crankshaft sprocket. Crankshaft sprockets used with stock GM timing sets are all powder metal. This is for noise reduction. So, what kind of sprockets did L-88 and ZL-1 use? Camshaft sprocket was wide nylon tooth. Crankshaft sprocket was wide powder metal.

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[Duke W.]

Re: Nylon Timing Gear & chain replacement

Duke-------


The roller links in this chain actually rotate whereas those in lower cost "roller" sets often do not rotate (that's where the name Tru Roller comes from).
One of the early symptoms of timing set wear/deterioration is the "jumping around timing mark" syndrome when using a timing light to set the engine timing.

That's the squishy part. Clearly as the chain moves across the sprocket there has to be some relative movement. Normally the roller is "locked" onto the sprocket and the relative motion is beteen the roller and the pin or the roller and bushing between the roller and pin. The other possibility is the roller rotates relative to the sprocket tooth, but that would cause rapid wear.

Like I say a roller chain is a roller chain and a roller timing chain functions the same as a bicycle or motorcycle chain.

I've seen lots of "spark scatter", and I always solved it by shimming up the distributor end play. I've seen a few cases where a timing chain may have been a bit loose from wear, and most of those engines had well over 100K miles. This even applies to the nylon tooth cam sprocket sets. They don't appear to wear much more than a cast iron sprocket, but they have a habit of suddenly shedding teeth causing valve-piston interference without warning, which is why they are a ticking time bomb inside an engine.

I've never heard of an OE Morse or roller timing set failing suddenly although I suppose it can happen, but must be extrmemely rare.

Duke

[Kenneth B.]

Re: Nylon Timing Gear & chain replacement

As I have said before those timing gears were crap. My brother & I both had new 1970 ones that failed a GTO & a Grand Prix . My brother in law was service manager for Packer Pontiac in Pontiac Mi. & said they were breaking all the time on new cars. I replace all of mine. I think it is the main reason so many Corvettes have CE blocks.

[Patrick H.]

Re: Nylon Timing Gear & chain replacement

Duke-------


I finally had to get them directly from Cloyes but they had a stiff minimum order. I bit the bullet and ordered a bunch of them. I got the wide big block, wide small block, and narrow small block [none for sale].

At least now I'll know why there's a box of them.

[Domenic T.]

Re: Nylon Timing Gear & chain replacement

By the way,
True roller chains did not have the slit on the roller. They were un-interrupted all the way around. We used to buy chain for the motorcycles at the industrial store until the refused to sell me one with the slit in the roller. Legal problems they had with bike accidents. Now I always inspect the rollers on my new chains, car or bike, to make sure that they have a true roller and not a rolled one with the cross ways slit.

Dom

[Dan B.]

Re: Nylon Timing Gear & chain replacement

Tim------


I have never had a problem with interference with the timing cover when using the Cloyes Tru Roller and I've never heard of anyone having such a problem. I've installed quite a few of these. However, while I've never had the problem, I've heard of a few folks that had a very slight interference with the block. Very minor relieving with a Dremel tool solved the problem. Since I've only heard of it a few times, I expect the root cause is excessive core shift in those blocks.

I fit everything and measured several times ( I prefer to do my own homework to verify) and surprisingly the clearance between the timing cover and the front of the new chain is nearly identical to the original. No problem with the timing cover. The extra width is oriented towards the block side which creates the narrow spot at 12 O'clock. That was too close for my liking even though it did not appear to actually touch. I felt it was better to grind it down a bit to allow some extra space for heat and wear expansion with a nice safety margin.

[Joe L.]

Re: Nylon Timing Gear & chain replacement

...extra width is oriented towards the block side which creates the narrow spot at 12 O'clock. That was too close for my liking even though it did not appear to actually touch. I felt it was better to grind it down a bit to allow some extra space for heat and wear expansion with a nice safety margin.

Dan------


That's exactly where the interference, if there is any, occurs with the Tru Roller timing set. Like I say, I've never had it occur but I've heard of it. Your solution for relieving it is exactly what I spoke of.

[Joe L.]

Re: Nylon Timing Gear & chain replacement

At least now I'll know why there's a box of them.

Patrick-------


They'll most likely still be there at the "final bell". I can't figure out what I would ever do with these things. But, they were hard-to-get so I just had to get them. I mean, it was just an absolute imperative! The folks at Cloyes told me that there is only one company in the world that makes these things or EVER made these things. They didn't tell me what the name of that company is but that's where Cloyes gets them and, without a doubt, that's where GM got them. I expect it's a company with a name we never even heard of.

[Joe L.]

Re: Nylon Timing Gear & chain replacement

The other possibility is the roller rotates relative to the sprocket tooth, but that would cause rapid wear.

I've seen lots of "spark scatter", and I always solved it by shimming up the distributor end play. I've seen a few cases where a timing chain may have been a bit loose from wear, and most of those engines had well over 100K miles. This even applies to the nylon tooth cam sprocket sets. They don't appear to wear much more than a cast iron sprocket, but they have a habit of suddenly shedding teeth causing valve-piston interference without warning, which is why they are a ticking time bomb inside an engine.

I've never heard of an OE Morse or roller timing set failing suddenly although I suppose it can happen, but must be extrmemely rare.

Duke

Duke-------


That's exactly how the rollers operate on the Tru Roller chain. And, as far as I can tell, not only don't they wear rapidly, they don't wear much at all.

In my case, the "jumping around timing mark" had absolutely nothing to do with the distributor end play. My original distributor had an end play of 0.060" when I removed it from the original engine. That's exactly the end play I've observed in EVERY NOS distributor I have (and, I have more than a few). So, I've got to assume that the end play I observed at the end is the same as the end play when the engine was brand new. Nevertheless, the "jumping around timing mark" began at about 10,000 miles and got progressively worse.

I rebuilt the above distributor without replacing the bushings and maintaining the end play at 0.060". I installed it in an engine equipped with a Tru Roller timing set. After 100,000 miles the timing mark when timing was just as solid as it was on day-one.

[Duke W.]

Re: Nylon Timing Gear & chain replacement

"The other possibility is the roller rotates relative to the sprocket tooth, but that would cause rapid wear."

Duke-------


That's exactly how the rollers operate on the Tru Roller chain. And, as far as I can tell, not only don't they wear rapidly, they don't wear much at all.

...never heard of that before. I suspect something is amiss. It's certainly not the way any high speed chain operates, like a motorcycle chain. If the rollers can be rotated then they lock onto the sprocket and rotate relative to the bushing or pin. To operate as you say the roller would have to be fixed to the chain lengths and not rotate. I'm sure you have some around. Check 'em out.

Duke

[Duke W.]

Re: Nylon Timing Gear & chain replacement

By the way,
True roller chains did not have the slit on the roller. They were un-interrupted all the way around. We used to buy chain for the motorcycles at the industrial store until the refused to sell me one with the slit in the roller. Legal problems they had with bike accidents. Now I always inspect the rollers on my new chains, car or bike, to make sure that they have a true roller and not a rolled one with the cross ways slit.

Dom

A chain with a "split roller" as you describe would only be suitable for low speed, low load service like opening big shop doors or low speed machinery. You were crazy to use such low rated chain on a bike, on or off-road.

Maybe you meant a replacement chain with a master link. When I replaced the 530 O-ring chain on my CB1100F some years ago I could have bought generic 530 O-ring chain, cut from a spool to the proper number of links minus one, and then used a master link and clevis to tie the ends together. But since my butt is on this 110 HP machine at up to 150 MPH, I bought a proper continuous chain that had the proper number of links with no master link. Just to be sure I bought the replacement chain from Honda, but got a discount from a buddy who worked for them at the time.

Some things are just not worth taking a chance on to save a few bucks, especially if it may put your life in jeopardy.

Duke

[Joe L.]

Re: Nylon Timing Gear & chain replacement

"The other possibility is the roller rotates relative to the sprocket tooth, but that would cause rapid wear."







...never heard of that before. I suspect something is amiss. It's certainly not the way any high speed chain operates, like a motorcycle chain. If the rollers can be rotated then they lock onto the sprocket and rotate relative to the bushing or pin. To operate as you say the roller would have to be fixed to the chain lengths and not rotate. I'm sure you have some around. Check 'em out.

Duke

Duke------


Yes, I have several. I checked this one out. It's a 9-3100T. The T suffix indicates that it includes a roller thrust bearing. However, the chain and crankshaft sprocket are identical to the standard 9-3100. The camshaft sprocket is the same except it's machined to accept the roller thrust
bearing.

After carefully examining it, I can absolutely confirm that the individual roller links on this chain definitely rotate. Absolutely no doubt about it, at all. Of course, the photos I am posting cannot show that.

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[Joe L.]

Re: Nylon Timing Gear & chain replacement

More photos:


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[Joe L.]

Re: Nylon Timing Gear & chain replacement

And one more:


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