Note: This article is contributed by EB, our local machinist-in-residence.

I keep seeing the same problem with the same causes over and over. About 1% of new timing chain installs fail, pick any brand.

So here are some "Don'ts" instead of a "Howtos."

The problem we see is the chain running loose and noisy, if left without correction the chain eventually breaks or the guiderail, yes, even a steel one, will snap.

Chains very rarely just "break", there is always a cause.

Typically one of the
following is the reason:

1. The top left oil upper pump holddown bolt protrudes through the cover, this jams the tensioner arm. (Wrong bolt, too long, common error)

2. The tensioner holdown bolts are over-torqued(12# is suggested) the shaft housing is measured in clearences of fractions of a thousandth of an inch. Distortion is the result of over tightening, this jams the arm as the engine warms.

3. Dirt, debris, silicone, sealers, tiny metal or plastic filings, same result. Cleanliness is a requirement here, be sure to clean the oil pan, too.

4. Resurfaced head/block results in added extension of the tensioner. Of course the oil fed tensioner is simply a hydraulic reservoir, too much surfacing defeats the oil
hydraulics and failure results. If the tensioner arm is overextended at rest, you must use a thicker head gasket or replace the head if the thicker gasket is not enough to correct. About .040" is the maximum possible to remove when combined with a thicker head gasket, even at this maximum your camshaft will retard by around 2?, not a happy situation but runable.

5. Lower than normal oil pressure/obstruction of an oil galley.

To identify a loose running assembly, note excess wear on nearly every other
tooth, and heavy wear on the tensioner arm facing. If present, you have a misassembly/install error. Of course a defect is possible, we have had tensioners handed to us "leaking" out of the back access hole plug. Of course, not enough oil could leak there to be of a concern, I check new ones and the ALL leak a tiny amount there.

Defects are rare but obvious, the shaft does not slide freely when operated by hand. If it does not or even feels funny, don't put it in.

If converting the stock type nylon driver's side gaurd to the heavier steel type, it is best to use a fastner like a couple of old oil pan bolts. While the nylon design does float slightly, the steel guide needs to be secure. (Yes, I know, our kits don't as yet have those fastners, I am working on that.) Suppliers can be stubborn.

Note that the steel guard does come in two designs, one has the holes for the late engine only, one design is drilled for both early 83-84 and the late. I personally don't like using the dual drilled piece on the 83-84 engine, I say it is too short but what do i know?

The problem with the dual drilled piece is it can be tipped slightly, this places the bottom of the steel gaurd closer to the chain as ir rotates around the crank gear. if running loose for some reason, it can catch which spoils your weekend.

Everyone who owns one of these vehicles will sooner or later deal with a timing set replacement.

Hopefully this piece will help reduce the 1% or so that diagnose a "defective" tensioner after a disaster.....*EB

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This is a torque tech document, also by EB:

>>*Other than simple overheat, the #1 cause of head gasket failure is clamping force variations.
Usually when I mention this, the answer is "I torqued it properly!"
*Yes, very likely, but torque, which is a twisting force, means almost nothing when we are talking about clamping force.
Dirt or machinery debris in the bolt holes will throw the clamping force off as much as 50% and more, even though the torque wrench reads perfectly normal.
The same happens when installing new bolts. The very best bolts made will show a rough mating surface at the threads when inspected under a microscope.
When installing new or used fastners, first be sure the bolt will spin in and out ALL THE WAY freely with simple finger pressure. Be sure they are lightly oiled, not too much which can hydraulic lock at the bottom of any blind holes and spoil your day.
Use this simple breakin procedure for any new bolts: Tighten all of them to 50%, back off 1/4 turn, then to 75%, back off 1/4 turn. Then take them to 100%, back off 1/4 turn and repeat. Do a retorque after full warmup.
*This procedure simply assures that the imperfections of the threads seat to the bolt hole threads.
Yes, time consuming, but much faster and less costly than another set of gaskets, the actual clamping force will increase vastly, even though the torque load is exactly the same.
The alternative is you may be additional twisting at the top of the bolt after the threads have come to a stop from excess friction.
If any single one does that, head gasket failure prematurely is gauranteed, plus it weakens the bolt....*EB

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Question: The tensioner holdown bolts are over-torqued (12# is suggested); is 12# the recommended torque for the t-chain rails as well? Thanks.

>>>*That really isn't critical, all that part does is hold the guiderail in place. Note the nylon style guiderails feature a shoulder style fastner, the reason is to keep from crushing the rail.

The steel design simply needs to be secure and properly located to clear the chain at all points at rest....*EB

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Premature TC failure Dropped In For Reference

Question We replaced the timing chain in an 86 22R, this included a head gasket set. After 1407 miles the chain snapped. Recommendations Suggestions?

Answered by EB
I have a dab of experience with timing chains on these engines, and have searched the world for the best suppliers. Quite simply, there are none that I would not consider using, and some I would prefer.

Unless there was a defect, (A possible scenario with any supplier) then something likely went wrong to cause the chain to snap.

*Look carefully at the gears, and at the passenger side guiderail and tensioner pad faceing for excess wear. If you see excess wear on every other tooth, the tensioner was not operating properly for some reason. This also shows as wear on the pads and guiderail.

We supply right at 100 timing sets every three weeks for the 22R/RE engines, we use M66 chains and they test to as good as any made. I know this for a fact because I was in the factory and sat in on some load/reversion tests, quite simply I can pick the entire front end of your vehicle off the ground with an M66 chain, in a pinch even tow it home.

But then we can do exactly the same with the Tsubakimoto, OSK (branded) the GCI, Sealed Power, Federal, on and on, all within 2% of test specs. The fun part is the Dual roller chain, which some love for it's "added" strength, fails at EXACTLY the same pull loads.

Yet we still see 1% fail, and normally early after an install. The chain WILL break if sideloaded, or if it is striking somewhere it should not be due to slack.

I would suggest you check to see if the oil pump mounting bolts got mixed up during install. If so, any long bolt will restrict the tensioner pad, interfere with it's operation. The result will be noise at best, and chain/guiderails/tensioner failure quickly, with the chain finally breaking.

*Now the bad part: Very likely, even at idle, you will have bent some or all of the valves. Replacing the timing kit won't fix this, the head will need to come off unless you are very lucky to fix the bent valves. Hopefully the timing cover won't be damaged, but if it is, you must replace that also.*EB

Inspection Results
We found 5 broken teeth on the lower gear; no marks on oil pump-drive and timing cover had a couple of scratches. Both plastic chain guides in mint condition, and best of all, not a single mark on the piston tops or valve bottoms.
This one-this must have been one of those in the 1% or less range- the chain must have been defective as upon inspection the link seemed to have stretched in the area where the pins tie it to the next link, all except one tiny piece of the chain were in place?

Reply Possibility
Now I know what did happen, and this is one sure way to break a chain. The key here is the "broken teeth" on the lower gear. Now this is a little bit of "Which came first, the Chicken or the Egg?".

We know that there is enough force in one single power cycle to actually move the entire vehicle down the highway at speed. We know that the instant the chain breaks, there is no more power.

Therefore the gear broke first, the tooth rolled over, the chain now has to reach around an impossible distance and gets loaded at and angle at the same time. The weakest link (where the hole for the pin goes in the side link usually) lets go.

Diagnosis is not a defective chain, it is a defective lower gear.

The lower gear is a casting, it needs to be for rigidity. This type of gear is then heat treated to harden it for wear characteristics.

So: Someone missed on the heat treat and got it too brittle..(I happen to KNOW this happens) or...someone putting in on felt it hang up a bit on the crank key and "helped" it into place with a handy hammer (the tiniest burr on a gear tooth is a guaranteed chain failure). Or...the warehouse person who is packing the kits dropped it on the concrete floor, then picked it up and stuck it in your kit.

I would hazard a guess the gear failed first....*EB