TR2/3/3A Moss Crankshaft pulley failure

I installed the Moss narrow belt conversion a couple of years ago ( maybe 1000 miles ago.)
"837-508 or TT1132 Pulley & 3/8 Inch Belt KitConverts TR 2-4 Four Cylinder Engines to 3/8” Fan Belt "


It worked great.....right up until it failed.

Three questions here:
1) has anyone else had a similar problem with their vib. dampening pulley?
note in the pic: the metal failure at the woodruff key slot and the reaming effect of failure.

the pulley bolt was snug & tight.

2) what do I do if the crankshaft end is ground down also ?( like the pulley boss)

3) anything I could have done different to avoid this?



Thanks for for any advice.

I really don't know any specifics about the Moss conversion...just dampers in general. The center bolt that holds the damper on most cars is installed insanely tight. Many modern cars only use the bolt once, as they are installed with up to 800 ftlbs torque and are permanently distorted after a single installation. The key locates the damper, but the tension in the assembly is what actually prevents the damper from slipping. My initial thought is that the bolt was not tight enough.

That said, the balance of the damper is very dependent on it's centering on the crankshaft nose. If you go to install a new damper and it does not go on the crank at least snuggly...then I'm afraid the crank will have to be replaced. If you install a damper with a loose fit, the chances are good that a crack will eventually develop, or the damper will slip and fret the crank even worse, eventually shearing the keyway. I would actually be more inclined to use a crank with a buggared keyway than I would a loose damper fit. Again, that is because the union is held by the torque of the bolt, not the key itself.

Again, I don't know anything about the Moss conversion. There may be more details in the instructions.

That's a bummer for sure. I'll try to help with a few suggestions...

1) I've had a narrow belt conversion on my TR3 for about six years, however, I bought it from British Frame & Engine. Most likely the same set that Moss is offering, but have no way to verify that.

2) This is a conundrum...If your crankshaft is wallowed out, then something will definitely have to be done, but it might not require removing the crank and repair or replace. The first couple of years of the Mazda Miata had a crank/pulley issue that is quite similar to what has happened to you. Some engineer worked out a "fix" that worked surprising well. Rather than explaining it, I post a link below and you pick out and see what parts are relevant to the TR. Basically, it uses a special Loctite formula that fills in all of the missing metal in the crank. Like I mentioned, this repair has generally worked very well on the Miata problem. You will of course need a new crank pulley and key. The other alternatives would require removing the crank and either replacing or getting welded up and re-ground. Might be worth trying the Loctite repair. If it doesn't work, all your out is some time and a few bucks.

3) Don't know what you could have done to avoid this other then making sure the the three pieces (crank, key and pulley) all mate well. The key should fit snug in both the pulley and crank, and the pulley should fit snug on the crank. No real discernible slop. And of course, the bolt holding it on should be torqued properly.

Link to Miata crank repair....https://www.miata.net/garage/LongNoseRepair/index.html

I am not sure what I am seeing in the picture, so forgive my confusion. I would go back to a stock set up. For my way of thinking a tr3 does not really have a vibration dampener, just a big 2 piece pulley on the bottom with some rubber around the fan mounts. Maybe there is enough meat left on the crank key way to hold the pulley hub and the bolt that tightens to about 150. The hub is long and beefy like most things on a tr3, but you would have to get a good look.
steve

In retrospect. I wish I would have stayed with the stock set up. But she was overheating badly.
now I'm pretty well committed.
pulled the apron & radiator this pm. The shaft looks ok but I may have to grind out the remainder of the woodruff key.
Moss has a two year warranty on this part. I am outside by four months, but they are considering my case because I didn't install it immediately.

Steve what you were look at was the key channel in the pulley boss, with the external spacer as the outer rim.
the spacer, btw, makes visualizing the line up of woodruff key impossible, all you can do is mark the spacer and line the mark up....less than ideal.

When I changed to the narrow belt I got many things from Ken Gillanders, including a crank pully. His advice and products are all top notch. I hope he's still doing business, as he's a monster of TR2 - 3s. Lots of knowledge there.

Thom
1959 TR3 #TS34909L(O)

Crank pulley failures occur on 1990-early 1991 Miatas, and there's a well-established fix for the problem. Go to Miata.net and search for "SNC failure" or "Loctite fix"

Is British Frame and Engine still around? I tried to contact them via the contact form on the website and got no response.

groupdeville said:

Is British Frame and Engine still around? I tried to contact them via the contact form on the website and got no response.

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Ken sold BF&E last year to a fellow enthusiast and supposedly all's well. I haven't done any business with the new owner, so I don't know how he conducts his business. Did you try the phone number on the site??

Just to be the advocate, if overheating is your problem and your radiator is clear, I would go with a Macy’s fan and swap back the water pump pulley and generator pulley. But you probably have an alternator and some other deals I am unfamiliar with.
steve

Here is the crankshaft post.
it is slightly ground down or at least slightly roughed up.


i was able to remove the broken off remains of the woodruff key.

That's the sign of fretting on the end of the snout and on the oil slinger. All you can do is try to install the new balancer and see if it fits snugly. If it doesn't fit without play, it will be a short lived fix if you just button it up and run it.

It appears the balancer does not ride on the snout all the way back to the oil slinger. A different design pulley/balancer may extend the contact surface farther aft and provide a good fit on the undamaged snout surface. Replace the slinger, or at least sand it on a glass plate to remove the fretting. The balancer must ride tightly against all surfaces, and the fretting will hold it off.

Unfortunately, I wouldn't give the crank much hope, but there is at least some hope...

Moss is going to provide warranty parts, so I may as well try a redo, using the Miata /loctite fix.

the moss specs only called for 60 ft/lbs. torque on the crankshaft end bolt. I'll bump that up to whatever I can get.

the woodruff key provides some clues to the root of this problem.
2/3 of the key is sheared off, meaning only 2/3 of the key was in the pulley boss channel, even though the pulley was snugged all the way in.
Reason: the pulley boss is to short, but the required spacer hides that from view
(the spacer increases diameter of pulley boss to form an oil seal, & extends well past the boss) .

I remember, when I ordered this part, the Moss rep. Telling me they use this same pulley (without spacer) for MG's. So it really wasn't designed for these engines.



Another potential issue is my crankshaft may not be original. Though I'm not sure about that.

OMG! 60ftlbs is WAY low. Measure the bolt and I'll look it up. From memory I would think it should be north of 100ftlbs.

GTP1960 said:

I remember, when I ordered this part, the Moss rep. Telling me they use this same pulley (without spacer) for MG's. So it really wasn't designed for these engines.

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That's the same that I was told by Ken at BF&E when I got my narrow belt conversion from them. They have been using the MG damper with the seal spacer for a long time on the TRactor engines. It is a proven, viable modification.

CJD said:

OMG! 60ftlbs is WAY low. Measure the bolt and I'll look it up. From memory I would think it should be north of 100ftlbs.

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The bolt is 5/8"-18 UNF...the service manual shows 140 lb/ft

Whew...the hair on my arms stood up when I read 60! I've seen what a damper can do when it comes off at speed from being installed too loose. It's like a saw that cuts through everything it hits on it's way out.

Edit: Oh, just remembered...

To use 140ftlbs, make certain that 5/8" or more of the bolt can be threaded into the crank snout. With the aftermarket damper you may have to use a custom length bolt to ensure you have enough meat to torque it down without stripping. Also, if you cannot use the factory bolt, use only a grade 8 damper bolt.

I was sitting here thinking. The last damper I installed was on our 2004 Range Rover. Get this...you torque the single use damper bolt to 120ftlbs, then turn it 60 degrees further, then another 60 degrees, and then turn it an additional 60 degrees further! I have no idea what the final torque was, since it had to be above 400ftlbs...but I had to use an 8 foot cheater and 400lbs of fat friends to get it there! On the first attempt I broke my 3/4" drive breaker bar. Thank goodness for Craftsman lifetime warranties!

A damper bolt is nothing to play around with.

As I recall, the center bolt should snug the middle part of the pulley all the way back to the slinger, pinching it HARD against the timing gear. This apparently did not happen or the damage from rotation of the damper on the crank would extend all the way back on the snout of the crank to the slinger. Is there a spacer that should have been in the kit that was omitted in the install? I fear that if you go back up with the same parts you will get the same failure in a fraction of the time. If this crank is at all salvable, you should probably go back with the original ungainly system. Another possible contributor to the failure would be that the keyway in the after market damper might be a little wider than the width of the key.
Bob

CJD said:

OMG! 60ftlbs is WAY low. Measure the bolt and I'll look it up. From memory I would think it should be north of 100ftlbs.

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here's what the Moss instructions say......I was to dumb to know better.

"

1. 17) Use the provided bolt (1e) and washer (1f) and pull the pulley into place on the crankshaft.
   
2. 18) Tighten the bolt to about 60 ft/lbs. Some people like to use Loctite on the bolt but this might cause future
   problems if the engine needs to be dismantled. The original bolt was tightened to a higher torque
   specification because it had a fan and hub extension to secure, and it was fighting against a stiffer belt."