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what's this junk in my cam housing?

Finally worked up the nerve to wade in after my motor stopped suddenly one day in late December. I was driving nice and easy on an open road when the motor shut down without noise or vibration. I clutched in immediately and pulled over. Got a tow.

I drained the oil, which looked clean. No flecks of metal, metallic sheen, or discoloration. The ends of all 6 rocker arms on the passenger side had snapped off. I thought it might have been a tensioner or timing chain thing, so I pulled the cover off of the passenger-side cam housing to find this:




Note the loose bolt to the left of the tensioner and the small pile of stuff that fell onto the paper towel.



I'm guessing the bolt is from the plate that covers the cam and the other pieces are lock plates from the oil pump. Any idea if that's what these are and how they ended up here???
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Old 01-29-2018, 05:39 PM
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those 3 lock tabs are ment for the oil pump nuts..
Old 01-29-2018, 06:03 PM
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Bolts that secure the intermediate shaft gear came off? Or one did and then got caught in the chain and caused it to break?

Someone used oil pump lock tabs on the bolts that secure the gear on the intermediate shaft? The bolt in the picture had some serious stress on it before it let go.

Sorry to hear about this.

Last edited by stownsen914; 01-29-2018 at 06:15 PM..
Old 01-29-2018, 06:08 PM
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My first thought was the oil pump locking tabs, but the intermediate shaft gear uses the same lock tabs and that is much more likely.

Not sure what the initial failure was, either way it will need to come apart for inspection.
Old 01-29-2018, 06:28 PM
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The cam sprocket teeth are quite worn indicating high mileage.
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Old 01-29-2018, 07:08 PM
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Thanks, guys. The threaded section of that bolt is seriously messed up. The head looks like it got caught in the sprocket. Sprocket teeth look pretty good though... I fear carnage in the bottom end.
Old 01-29-2018, 07:09 PM
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Shouldn't there be two more bolts to go with those two locking tabs?
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Old 01-29-2018, 07:15 PM
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Quote:
Originally Posted by manbridge 74 View Post
The cam sprocket teeth are quite worn indicating high mileage.
Edit: Cam sprockets, chains, etc... have maybe 8-10k miles on them. Tensioner sprocket has maybe 14k miles.

Last edited by Baby; 01-29-2018 at 07:48 PM..
Old 01-29-2018, 07:38 PM
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Maybe itís a trick of the light but the valleys do not appear symmetrical. Compare below.


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Old 01-29-2018, 10:21 PM
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You are going to be splitting the case. Then all will be revealed. Good luck.
Sounds like it had some recent work?
Alan
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Old 01-29-2018, 11:42 PM
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Based on the evidence, the very excessive wear on that idler gear, and the speculation wisdom already shown, my guess is this:
The bolts holding the intermediate shaft aluminum crank gear to the shaft hub weren't properly tightened, so started loosening despite the lock tabs. In some way I can't explain, this essentially misaligned the right side chain and its three gears - drive, idler, and driven, leading to the wear which is unusually prominent on the idler. Then when a missing bolt got into a place where it locked something on the right side, that chain snapped.

Assuming the left side rockers didn't also break, probably meaning the left side chain didn't break, somehow the IS crank gear was held into its rotational position somehow - I can't recall if there are three dowels along with the three bolts?, that would explain the one sidedness, given that all three bolts backed out.

Anyone seen those bolts back out? I don't think that is a common problem after a rebuild. Finger tightening fasteners and forgetting to finish the job happens often enough, but it sure looks like the locks were tapped into their functional position - unless they were reused and not reset?

I'd have thought misalignment of a chain to that extent would cause one hell of a racket. One engine builder told me that you can easily hear if you are more than one shim off on this alignment.

A right side valve check at a minimum may well be in order. I can't recall just what I had to replace when the teeth on my IS gear stripped at full race song and all 12 rockers broke simultaneously, but it is a lot to expect that none were bent. You can do a leakdown - don't even need to rotate the crank! easily enough for a quick check on that side.
Old 01-30-2018, 05:41 PM
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Thanks for your thoughts, Walt. I think manbridge is right about the trick of light. As beat as the cam sprocket looks in the photo, it looks prettymuch perfect to the naked eye. The idler teeth are a little more worn than the cam sprocket teeth, but it's symmetrical and it's nowhere near as worn as the one manbridge shows in his photo. That said, it makes sense, as others have said as well, that the bolts and tabs held the gear to the intermediate shaft. (I did find another loose bolt under the chain. Same as the first.) The second bolt was intact, with only a small nick on the threads. The first, pictured in the initial post, shows threads that are worn smooth on one side. So three tabs and two bolts. It's possible that there are still three bolts holding the gear to the shaft. And another bolt floating around somewhere. I'm not sure the chain was misaligned and the sprockets wore. The thing ran like a top: quiet, great oil pressure, great power.

Good idea about the leakdown! I'll give that a go.

In an earlier post I was off on my mileage: The cam sprockets, chains, cams, etc... have exactly 26,668 miles on them. (The po upgraded the tensioners probably 10k miles before the motor was rebuilt, so at least they're not all that old.) During the rebuild the oil pump was inspected, the oil cooler was tested, the crank was serviced and cross drilled at the #4 journal, new bearings throughout, etc... Cams got the 964 grind. New locking tabs were used on the intermediate shaft sprocket. Pics from the build show them properly installed.

Thanks again!
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Old 01-30-2018, 09:54 PM
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wow.... that's crazy! So did the chain break?
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Old 01-31-2018, 07:05 AM
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Quote:
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wow.... that's crazy! So did the chain break?
You bet!
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Old 01-31-2018, 11:06 AM
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Quote:
Originally Posted by Baby View Post
............ New locking tabs were used on the intermediate shaft sprocket. Pics from the build show them properly installed.

Thanks again!.........
It will be interesting to see the inside and to hear theories on how they could have come loose.

Thanks for sharing, we can all learn from your experience, however painful.
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Old 02-01-2018, 05:05 PM
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I'll definitely report back when I get somewhere. Next step is to pull the cis and intake off the motor and get it onto the stand. Meanwhile, I'll to get back into the spirit of all this...
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Old 02-01-2018, 07:17 PM
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