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Installation of the FBO-J685 Total Mechanical Timing Limiter Plate:

This plate will correct the mechanical limits in your distributor so now you've got 1/2 the job done. To make your ignition capable of burning the fuel efficiently and completely you still need to have a control box that is up to the task. The old 60's style transistorized ECU will take away all your efforts by retarding the timing by up to 8-10* under load. Old 60's style TRANSISTORS CANNOT keep up to today's fuel formula's or the rigors of modern camshaft grinds, cylinder heads and loads we put on these 2000's built engines.

You need to correct the spark retarding and output drop of these old antiquated and unreliable transistor type Ignition Boxes and step up to the HRR688 Computer Controlled system, eliminate the Ballast, 6V coil and get a REV Limiter on your engine... Not that I've Ever missed a shift (right) at 6800 RPM but I've heard rumors that it can happen. The result is not pretty and it's expensive! Protect your mighty Mopar against possible driver error. Rheostat type REV Limiters are NOT a dead stop control device and they DO NOT cut cylinders in an algorithm.

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1. These instructions are for FBO Distributors as supplied in our DIY Kits or any original Mopar. Will work in most as cast type Mopar distributors. 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!
***Stock Distributors usually have the wire clip.
***Some Aftermarket use a screw.

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.

One last step... Get an American Made control Box with a Algorithm REV Limiter that can keep up to your engines RPM and Load!

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