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Installation of the FBO-J685S Total Mechanical Timing Limiter Plate





1. These instructions are for FBO Distributors as supplied in our DIY Kits.

Be sure and mark the reluctor so you get it back on the right way up.  Also note the location of the roll pin some distributors may have 2 slots so mark the correct slot.

***Check Footnotes for other common brands

2. Using two flat screwdrivers gently pry up on both sides with equal pressure.  The reluctor will slide off.





3. Remove the 4 screws from the bowl.






4. The top plate is spring loaded so gently lift it up and at the same time push the vac arm pin down to release it.





5. Give the can a slight twist and the vac can will come free.






6. Now you can lift the plate out of the bowl.  Note the location of the alignment slot to the roll pin for re-assembly.






7.  Remove the top shaft

(You can see here that this distributor already has a J685S Plate installed.)

**Some distributors have a screw inside the top of this shaft and some have a small wire clip, these must be removed to get the shaft off.


8. Select the degrees of mechanical advance you want and drop the plate over the pins as shown here.

Before you drop in the plate you may want to change springs at this point.

Read the article in the Tuning To Win book on how to determine the RPM for all in.


9. Reassemble
  1. Top Shaft
  2. Pick Up plate assembly (Align slot with roll pin)
  3. install 2 screws for the Pick up plate.
  4. Install Vac can & hook pin into plate.
  5. install 2 screws to secure vac can. (Align roll pin with hole)
  6. Install reluctor (align roll pin to slot in top shaft)
  7. Rotor (Twist to Check for smooth operation)
  8. Snap down the Cap and go!





10. Good Job!

Now set the timing.  Your initial timing will be 34 minus (Slot number) = initial

Slot 18*- Initial 16

Slot 10*- Initial 24* and so on.

Now plug in the vac can to CONSTANT Vacuum and see where it pulls the timing.. it should go to about 30* for most applications.  If not use a 3/32 Allen wrench and adjust the vac advance unit until you get it to about 30*

Once you get the timing events all correct you can proceed to adjusting the carburetor.

Carbs are adjusted with the vac line connected to the Constant source.

Stock Distributors usually have the wire clip

Some Aftermarket use a screw