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MSD Distributor Upgrade

Posted in How To: Engine on March 1, 1999
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If you're tired of your old AMC V-8 distributor-or, more likely, it's tired-MSD has a replacement unit that's really a treat. This is especially good news to the Jeep contingent; those who run the 290-304-360-390-401 family of AMC engines know there aren't a lot of options available.

When Jeep started using the AMC engines back in 1972, they were fitted with a GM points-style distributor, which used a standard GM cap, rotor, and guts in a special housing to fit the AMC engine. Though still a popular conversion for those who need a reliable distributor, they are nonetheless rebuilt units that may need some tweaking.

After the point distributor left the Jeep world, along came Prestolite electronic ignition distributors. This sad little unit has little if anything to say for itself other than treating parts stores to healthy profits. After the Prestolite debacle, AMC decided to use the tried and proven Ford Duraspark electronic ignition, which, with a few variations, was used in fullsize Jeeps up to their discontinuance in 1991. A simple magnetic pickup in these distributors sent spark information to the control box, and efficient ignition was available. These control boxes have been known to last well over 100,000 miles, even though a spare should always be carried.

The distributor itself can develop wear in the shaft and bushings along with horrific endplay problems. These problems can cause erratic ignition timing and prove disastrous if the engine has been built up, and spark placement is critical.

The solution to all the worn-out or antiquated parts is a new distributor, and MSD got it right from the get-go. The MSD unit uses a simple magnetic pickup-in fact it looks identical to the Ford unit. But billet aluminum is used to craft a one-piece housing, the flex and fitment problems are gone. Oversize bushings ensure long life, and the standard-size points-style GM cap and rotors means parts can be found almost anywhere.

The first step to swapping a distributor is to unhook the battery cables. That way, the rotor-to-camshaft relationship can't be altered accidentally by your buddy cranking the engine while you're not looking. To get things properly aligned, pull off the distributor cap and mark to which tower on the cap the rotor is pointing. This will be the same tower on the new cap once the wires are swapped.

The only dilemma with the MSD unit is that it must be used with the MSD ignition boxes, or so the instructions and ads indicate. That's fine if you have the dough and need to upgrade the whole system anyway, but what if you have the Duraspark system and only the distributor is bad? We took a close look at the MSD unit and talked to a few of the company's engineers. We realized that the magnetic pickup is virtually the same as the stock Jeep/Ford unit, even down to the same color-coded wires.

What follows is more than a how-to about installing a fancy distributor. It's also a primer on how to figure out some basic electronic ignition theories. The details we came across can help regardless of what engine you're slapping a sparker on. New box or not, the MSD distributor can help you tweak a bit more ponies out of your old Jeep at about the same cost of a lot of worthless add-ons.

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