borland

To aid with swapping out the cam gears/sprockets on my 90' S4, I made this cam sprocket alignment tool. My car uses the later model cam gears with the deep notch on the front side. The tool was pretty easy to make.

This DIY tool allows for accurately swapping out sprockets that are already assumed to be in alignment or for making timing adjustments. However other methods (PK32V’r, scribe marking, or digital caliper) can be suitable for this too.

I calibrated my tool assuming the cam sprockets were in alignment, but calibration could also be by using the dial gage procedure of WSM volume 1, with the cam cover(s) removed. Turns out on my car, both left and right sprockets showed the same settings relative to the cam keyways.






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For the cam sprocket alignment, WSM calls for using three M5x15mm bolts to hold the sprocket in place while tightening the center M10 bolt. I used M5x16mm socket head cap screws. The tool is held aligned in place using two of these bolts and two ¼” drive 4mm hex bits.

To avoid parallax reading errors, the scale uses dual tick marks. Minor tick marks are every 1 degree of cam rotation. The scale's two darker tick lines mark the sprocket’s deep notch. The "double arrow" marks the location for the TDC#1 cam marker, while the "single arrow" marks the adjacent tooth. Aligning the sprockets using two markers provides greater readability accuracy than with using just one.

To make the tool, I punched the alignment holes using a 5/32” hole punch. These holes are just slightly smaller than the 6mm bit, so I needed to further widen the holes using the 4mm hex bits.

The scale was printed using a laser printer then cut out and glued to the aluminum sheet with rubber cement. For the scale, I used this web site to generate a polar plot…

http://www.incompetech.com/graphpape...ularpolar.html

configuring the web page parameters…

- 9 concentric circles
- 36 primary spokes
- 360 secondary spokes
- line color black

Then using Acrobat, I added the tick marks and arrows.

Here's a look at the full page generated, then a closeup of the area needed to be cutout with scissors and glued to the tool...