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I'm running the Mopar electronic dizzy with orange box. Big cam wants a lot of initial timing to over come off idle stumble. Now i need to restrict mech advance to stop the pinging. Motor likes 20to 22 degree's of initial advance.

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The solution is quite simple. The problem occurs in varying degrees in all performance applications. The way to get around this problem is you set total advance. This means that you set the "30 degree" number for total advance instead of the 12 degree initial number. Initial advance is set at idle (1,000 rpm or so); however, total advance is set at the point where the centrifugal advance reaches its maximum (the advance curve goes horizontal). With a performance curve (see Figure 2 112) this means 2,000 rpm. With a production curve, this rpm would be around 5,000. So with a production curve in the distributor, stay with the initial setting method. (The maximum power, total advance number varies from engine to engine.)

For our performance and racing applications, we now know how to set our timing correctly and why. The next question that comes up pertains to the vacuum advance system. In our initial discussion we assumed that the vacuum advance was zero. Now we'll add it into our analysis.

The first item and most important thing to realize is that vacuum advance does not affect the previous discussion. Vacuum advance is an add on device designed primarily to increase fuel economy. Race distributors don't even use vacuum advance. However, most people have a distributor with vacuum advance, so we'll cover this to remove the mystery.

The basic operation of the vacuum advance is quite simple, Vacuum advance increases the amount of spark advance in high vacuum conditions, Realize that we race at W.O.T. (wide open throttle) which means zero vacuum. So the vacuum advance doesn't affect our performance at W.O.T. Figure 2 114 shows a typical vacuum advance curve. Note that in a high vacuum (12 inches of Mercury) the advance is approximately 16 degrees. This means that in a high vacuum condition (cruising, coasting, etc.) we can have 46 degrees of advance (30 + 16). As we open the throttle the 16 number drops until at low vacuum (approaching W.O.T.) it goes to zero.

Vacuum advance units vary greatly from year to year and engine to engine. One of the characteristics of Chrysler-Plymouth Dodge electronic distributors (not Lean Burn) is that the amount of vacuum can be adjusted. By inserting a small Allen wrench into the vacuum tube and rotating it, the amount of vacuum can be dialed out. In other words, the 16 degrees built into the vacuum unit can't be increased, but you can adjust it to any lower number desired. You can adjust it to be zero which would mean it didn't work. Generally, we wouldn't recommend this approach. If you don't want it to work, just disconnect the vacuum hose. When setting your timing, if you have a vacuum unit on your distributor always pull the vacuum hose off and plug it (usually with a handy bolt). At this point it doesn't work (zero add in advance) and won't affect the total advance setting.

Now you should completely understand spark advance. However, recurving distributors usually requires a distributor machine. Spending time assembling and disassembling distributors and running them on a distributor machine gets expensive. The easiest, and in most cases, least expensive way to get the same result is to get a Mopar Performance Parts distributor which is already recurved (P3690427, P3690428, P3690431, P3690432). It has the performance curve shown in Figure 2 112. This gives you the performance curve, adjustable advance, and electronic triggering all built in.

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Not sure how you go about doing it? What is the process?

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pull the felt out of the dist then w a long thin set of needle nose pliers reach in & open the pliers backwards to open the vertical nubs on the clip a bit then grab one nub & pull it sideways(in the direction to open it) and up & out all in one motion then with 2 large screwdrivers opposite each other(carefully)lever the reluctor up(& you'll have to change the screwdrivers to larger pry bars)as the reluctor moves up till it's off the center shaft then take off the 2 vac adv mounting screws & lift the plate inside slightly & unhook the arm from its hole & remove the vac adv then the 2 screws on the outside of the housing for the 2 parallel flat plates & lever them up/out. Now you can take out these plates & you want to (not JB )weld the 2 slots then open each slot w the right size rat tail file to .365 (for 7.5 dist degrees for a SB) or .375" (for 8 dist degrees) for a BB. That'd be a very good time to change your springs and take out the yellowish plastic bushing and the 2 weights & solvent rinse then dry everything inside then lube the 2 holes in the weights and the pins that the slots in the pic fit into and the center shaft all along its length and the plastic bushing. I use silicone clear grease as it seems to collect dust less and the chamfer on the plastic bushing goes down and also remove the triangle snap ring thingy to seperate the 2 flat plates & clean them & lube the areas where the 3 "feet" ride).EDIT forgot the pic

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I havent owned one but I think they are adjustable w 2 torx screws that are in plain view on top of the plate so no you dont have to go thru all that dissassebly(& thats why they came up w that)

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I havent owned one but I think they are adjustable w 2 torx screws that are in plain view on top of the plate so no you dont have to go thru all that dissassebly(& thats why they came up w that)

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No welding needed.
The mp unit is adjustable, so it's easy to mess with. I've always had to pull them partially apart(remove the pu plate)to get access to everything. You can reach the torx screws with the plate in, but then it just slides wide open. Need to hold the slots where you want them, when tightening the screws.

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This is a new MP dizzy.

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...you want to (not JB )weld the 2 slots then

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Will I ever live that one down?