In for a rebuild kit if you get to that point, this job is on my agenda as my car eclipses 200k.

 

Here is the best cross section I can find for the 968 variocam. Dirty layout pictures to follow. I still haven't gotten the snap ring out of the smaller inner piston. Some of the O-rings are on order, but the wiper seal is going to need custom fabrication. Getting european spec o-rings for dynamic oil soaked applications, in the correct durometer, took quite a bit of research/searching.

As to function, the inner piston is what appears to provide the tension to the chain, not position up and down. It does this using the spring pressure, but its pretty low (I can tighten the mini puller by hand easily), there are oil circuits that bleed oil pressure into the inner piston. The larger outer piston is what changes the cam timing, by moving the "taut, short side" between the cam gears from one side to the other.

My lower cam pad has some impact damage, luckily I took it apart as soon as the noise became constant - no damage to cam teeth.

Can't seem to figure out how to post pictures, will try tomorrow

 

I still owe you all pictures of the dirty layout after disassembly, as well as pictures after wiping everything with acetone + tolulene based brake cleaner.

After chemical analysis and careful measuring, the square seal that seals the inner piston is going to cost about 200 bucks to have ten or so custom made (non standard OD and thickness). Took a lot of searching but have the correct dimension O rings in the correct hardness and material for the main piston in hand.

The second page of this Jackals Forge variocam inspection has one of the better cross sections of the 968 variocam. I have not been able to remove the innermost snap ring to get to the ~ 25 mm O ring inside of it. Can compress it with a quarter inch socket and the small gear puller am using, but the snap ring doesn't want to pry out, just rotates in its groove. Am thinking of leaving it alone but am concerned about its age (32 years).
Procedure for inspection of Porsche 968 Camshafts, Cam Chain, and Variocam Tensioner

 

Hope this scan from a couple pages in a training guide may be helpful to you. Its a PDF file. My scanner is of average ability and having to hold the spline down and one page at a time. This booklet is called Porsche Service Information Technik '92. As I understand it was given during training with the WSM to Porsche Techs.

 

944-105-507-00 are the 4x external guide pins the parts drawing is a bit misleading, it has nothing to do with the check valve

 

Here is a good video that helped me understand the 968 variocam and chain tensioner.

 

I'm getting ready to inspect and probably replace my pads and chain on my 968. I've read through the DIY's and they all state using 944 105 509 00 for the top and bottom. However, copilot swears the top and bottom are different and the 93 or 94 version of the PET shows the different part numbers for the top and bottom.

• The upper rail is long and straight → 513 00
  
• The lower rail is short and curved → 509 00
  

I am 99% sure the DIY's are correct but want to throw this out there to alleviate any questions in my mind. Usually when I disagree with copilot, it will correct itself. But it consistently states that they are different and the upper is omitted in the 95 version I have.

Thanks!
Rick

 

944 105 513 00 is not a valid Porsche part number. Your AI hallucinated it.

Quite alarms me that people are using AI for such things now...