Played with my timing and learned about
Started a new thread Tune up on a 285 / Weber Carburetor / Distributor / Timing / Advance / Discussion http://www.jeepforum.com/forum/f8/tu...ssion-1527457/
The centrifugal advance is your “Performance advance”. It is achieved by weights being thrown out by centrifugal force as the RPMs increase in the distributor shaft. This is controlled through different spring tensions on the weights and the limit of the opening in the slot in the advance plate.
1979 and earlier advance plates have two opening one for 13 degrees and one for 18. I got mine through Advance Auto as my son works there, you can also get one through NAPA part number NRD484691. You must open the box and check through the peep hole that the advance plate is stamped with 13 and 18.
After 1979 the slots were ___ and ___ which limited the advance with the idea of emissions in mind (I will expand on this). My 1984 computer controlled 285 was stamped with 6.75 and 7.75
By flipping the advance head around from the 13* slot to the 18* slot, you'll get more centrifugal advance out of it. The 18* slot is closer to what the engine really wants for solid performance where the 13* slot is more of an emissions-restricted setting.
1)It is best to remove the distributor for the vehicle.
2)Remove stator, don’t lose the roll pin, this can be done with a puller of a pair of opposing screw drivers. The puller will give you more control. It is not on very tight so it can be done with the screw drivers.
3)Remove pickup base plate, there are two different screws holing the plate on. One is conical and the other is a pan head. The pan head holds the ground strap of the wiring harness in place and the conical one goes in back of the pickup.
4)Remove advance springs. Placement of the springs does not matter; there will be two different tension springs (one bigger than the other).
One tab may appear bent but it is like this to keep the spring from falling off.
The light duty spring should have a small amount of preload to return the plate back to “natural” when the shaft is not spinning. The heavy one will be loose.
5)Remove small inside “C” clip in the top of the shaft to release the advance plate. This is hard to see and may be hidden under some grease.
6)Flipping the plate is a misnomer, you will be picking it up on the shaft rotating it to the 18 degree slot and putting it back in place. Slide the advance plate up on the shaft, rotate to 18 degree slot is aligned with the tab and set it back down in place. I took it off the shaft here so you could see it, but you do not have to do that.
7)Long tabs on the stator go up, careful not to lose the roll pin
Foot note. I found that the pickup plate was pretty tight so I took it apart and flatten the wafer washer a little and put a small amount of silicon grease on the plastic tabs, it now moves smoothly.
Additional foot note. In some of the mega threads it is recommended to adjust the vacuum advance diaphragm out 7 turns counter clock wise. i was unable to find the correct size allen wrench to do this.
I have been informed that the correct allen wrench is a 3MM wrench.
Just for the grins of it I went through the allen wrenches on the distributor that I pulled out and found one that fit. Tried it in the new one and it does nothing. I pull the vacuum of the old distributor and put it on the Modified distributor.
Let me know if this should be edited to include something else about the centrifugal advance.
Another foot note. I have taken the recommendation of going to the 18 degree advance at face value and did not test the 13 degree advance.