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Verify torque for camshaft sprocket bolt


waynerd

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So I remember kinda wincing when I torqued up the right side camshaft sprocket bolt - the torque spec listed in my Clymer's seemed a little excessive (48 ft-lbs) - but it snugged down OK. Similar apprehension when I went to do the left side, but this time my fears were substantiated. I snapped that bolt - classic elongation failure. The only bright spot was that I was able to easily spin out the remaining piece of the bolt from the camshaft (and also managed to keep from dropping it into the engine case).

 

So, is 48 ft-lbs the correct torque?

 

The BMW replacement bolt is surprisingly reasonable ($1.68). Can I trust it, or should I just go look for a grade 12.9 elsewhere?

 

Thanks All.

 

 

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So, is 48 ft-lbs the correct torque?

 

The BMW replacement bolt is surprisingly reasonable ($1.68). Can I trust it, or should I just go look for a grade 12.9 elsewhere?

48 ft-lb is 65 Nm -- the torque spec. I, too, was surprised at how high, but I've done a few and never had a bolt break. I would use the BMW bolt because you know it is (at least supposed to be) correct for the application.

 

Did you reuse the old bolt? I wonder if it was already stretched when you went to reinstall it (i.e, a reason to not be concerned about the replacement breaking).

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Thanks for the confirmation, Mark. I did reuse the old bolts - didn't think these were one-time use. I will get a couple on order. Just frustrated to lose momentum again on this rebuild. I appreciate yor input.

 

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You might want to check your torque wrench calibration.

 

+1. Also be sure to verify if the spec is dry threads or oiled.

 

Andy

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Morning Wayne

 

That 48 ft lbs (65Nm) is probably in the ball park as the standard torque spec on a M-10x1.25 (10.9) bolt is 76.2Nm (dry) & 57.2Nm (lubricated).

 

If a M-10X 12.9 bolt then 89.2 Nm (dry) & 66.9Nm (lubricated).

 

BMW manual bolt torque is given for engine re-assembly (after parts clean up )with no mention of putting lube on bolts so BMW spec is more than likely for dry bolt.

 

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Thanks all, for your replies. I've had similar concerns (torque wrench calibration, dry vs. lubricated threads). DR, thanks for the standard fastener torque #'s. They jive with the torque values that I have looked up. I don't know what class that BMW bolt is, but grade 12.9 is about the only version I can readily find in a cap socket head (Fastenal, McMaster). I will likely order both the BMW bolts and some generic 12.9 bolts for back-up...and be sure to clean & dry the threads.

 

Thanks much.

 

 

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Evening Wayne

 

If you are going to replace both side bolts then you might mike the removed (good) bolt & also mike the new bolt lengths to see if you can determine any stretch in the bolt you just torqued.

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  • 2 weeks later...

I installed the fresh bolts and they snugged up firmly - no queasy feeling this time as I approached the specified torque.

 

DR, I measured the old bolt (that did not fail) and I could not determine any noticeable stretch. There was as much variation between the two new bolts (manufacturing tolerances) as there was between the the old one and the new ones. All measurements of the three screws (thread length only - multiple measurements around the perimeter of the threaded portion) were within .007" (.18mm). I think the old one fell somewhere in between the two new ones.

 

All better - movin' on. Thanks for your replies everyone.

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