Making a 2.2 SOHC cam gear into a 2.0/2.5 DOHC gear

[douglas vincent]

How to convert a SOHC cam gear from the early 2.2 subaru motors (1990-1996) into a DOHC cam gear to fit either twin turbo DOHC heads, or 2.5 DOHC heads.

I recently had to convert a SOHC cam gear into a RS 2.5 Cam gear to fit a WRX head. Whooh.

I used a milling machine with a rotary table, and small lathe. Using a small lathe, I turned a section of brass that was 7/8 diameter on one end (to fit into the milling machine), turned the next section down to fit the center of the rotary table, and the tip of the brass to fit the cam gear center itself.

Then, after bolting the rotary table to the milling machine table, I mounted the brass centering piece into the milling machine, and adjusted the table until the rotary table was perfectly centered under the milling machine head. Then I mounted the cam gear (teeth down) to the rotary table, using the brass to have it centered perfectly in relation to the rotary table.

Then I swapped the brass for a 6mm pin. The cam gear locating pin had been punched out and was measured to be 6mm. I adjusted the milling table so that the pin now drops directly into the hole, but in a single axis (front/back). This means I move the mill machine table directly forward and rotate the rotary table till the pin and the hole meet.

Now I must rotate the rotary table counter clockwise 22.5 degrees (or 3 teeth). At this stage I could either swap out the 6 mm pin for a 6 mm endmill and drill a new hole (this would make the cam gear swappable for an early 2.0 or an early 2.5 DOHC gear). Or, if you need to make this cam gear fit a WRX head (as I was having to do), then switch to a 5mm end mill, and mill a slot back into the center. If you are making the drilled hole cam gear, then pull the cam gear out and punch the 6mm pin back into the new hole. If you are making a WRX gear, you will have to enlarge the outside dimension of the cam hole about 1/16th, which I did with a larger endmill.

After all this is done, you must move the timing marks forward 3 teeth. I used a razor blade and to scribe them.

Then your done!

And maybe I will take pictures next time…..

[turboleg]

Nice write up. Pictures would help a bit, but I think I get the idea.

I love "do-it-yourself" work!

[mikec]

I didn't follow that at all... Any pictures of the finished product?