Beisan or OEM upper chain guide

[Obioban]

Guess you can never say never, but I bought the car with 110k on it and a 3" thick binder of service history that never mentioned it having been replaced, and the PO thoroughly documented the vanos lockdown at 100k. Perhaps it was done then, but there's no record of it.

Regardless, the stock parts are clearly suboptimal and was glad to see an updated version was available when I checked it during the process of changing out rod bearings 3 years ago. Was a no brainer.

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I’d put money on that having been replaced with the vanos.

[Sprp85]

As my car is ready to hit 100k miles, I am contemplating tackling some of the maintenance items;

I know for a fact that previous owner of the car performed full VANOS overhaul using everything Besian & DrVanos parts back in 2016; But I do not believe upper chain guide was touched.

So, every time when I see pics of the broken upper guide, it gives me a bit of uneasy feeling.

A few questions... how involved is it to replace the upper guide? Can this be addressed during a RB job? What are the symptoms of it failing & what happens when that thinner-end breaks off? (Will this lead to a catastrophic failure?)

[sapote]

As my car is ready to hit 100k miles...
A few questions... how involved is it to replace the upper guide? Can this be addressed during a RB job? What are the symptoms of it failing & what happens when that thinner-end breaks off? (Will this lead to a catastrophic failure?)

If it's original then the guide tip is about to break off if not yet.

How involved? remove vanos, EX hub, EX cam sprocket. But before that, look to see if the tip broke off or not, then carefully fish it out and don't let it fall down into the oil pan -- means the vanos needs retiming after. This has nothing relate with rod bearing process, but if the broken tip already fell down in the pan.

If the tip broke off, the lower guide -- which the chain tensioner presses on -- will wear out faster as it now pushing the chain at a sharper angle. At very high rpm, lacking a functional upper guide, the chain could jump on the EX sprocket and engine damaged.