Cam sleeve bolts backing out: why this happened only on the Intake cam?

[sapote]

Another M3 with sheared off intake cam bolts thread on E46 Fanatics. I have not read a single case with EX cam bolts loose or sheared off. Why?

As the crank sprocket pulls and jerks on the intake sprocket to loosen these bolts, I think the EX side is dampen and shielded off by the leading Intake partner. Just my theory.

[mrgizmo04]

Tensioner helps ex

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[Slideways]

My initial guess was that there was a calibration issue with the torque wrench used to tighten the intake cam bolts at the factory. This would not make much sense if the same wrench was used on the exhaust side which never back out.

My second guess was poor engine operation by the first owner, but this also would not explain why the exhaust side never backs out.

It could be a combination of issues, IDK.

Earlier engines didn't seem to have this problem as bad as the later engines.

[sapote]

I still think the EX sprocket is dampen or shielded off from the IN sprocket/cam load. The chain top section between the 2 sprocket never under the tension all the time, which means the EX sprocket is pulled with less jerkiness than the IN sprocket, by the crank sprocket. Every time a plug ignited, the piston jerks the crank which jerks the Intake while the Exhaust has a little delay and be dampen.

I am thinking one easy way to keep the bolts from backing out, just like Nyloc nuts: add a section of heat-shrink tube on the bolt near the head as red colored in the pic. The shrink tube will jam the bolts to the spacer holes as Nyloc.
I will measure the clearance between bolt and hole (which is not threaded). This is easier than cleaning the bolts and threaded holes on the cam and Loctite.


Spacer alone:

[sapote]

Does the cam come with the splined sleeve? I can't find the part number for the sleeve and the above spacer on RealOEM.