They say you can’t have your cake and eat it too. Which means you can’t have it all at the same time. Building a 4x4 is the same thing. Big tires kill fuel economy and eat power. Big power loves fuel. And building for a low center of gravity and high ground clearance doesn’t usually work. But we found something that gives you the cake and lets you eat it, too: a new distributor in your old 4x4, specifically an all in one DUI ignition system from Performance Distributors.
The old points distributor has one thing going for it, and that’s its ability to keep sparking at low voltage on your battery and charging system. But this does nothing for performance of spark, and setting point dwell can be time consuming and frustrating. We decided it was time for more power in the punch for our 1972 Wagoneer, and that was coming in the form of a new distributor.
Most gas 4x4s from the 1960s and 1970s have points-style distributors, which can be low on spark at best and finicky to tune and keep sparking at worst. The DUI distributor is similar to the HEI General Motors distributor with a 50,000-volt integrated coil and low-amperage draw built right into the distributor so minimal wiring is required. And since Performance Distributors builds each unit with a custom advance curve tailored to your vehicle’s specifications, it’s like getting an ignition dyno tune thrown in. With just a little wrenching you’ll instantly notice an improvement in drivability and power, easier starting, improved throttle response, and a 1- to 3-mpg improvement over the old ignition parts.
The first step is getting your engine to top dead center (TDC) before you pull the old distributor out. We used this trick where we removed the No. 1 spark plug (front driver’s side) of our AMC 360 V-8. Then we whittled down and screwed this cork into the plug hole and bumped over the engine with the starter until the cork shot out. It will come out with some power and shoot across the shop, so don’t stare at it. This gave us TDC on the compression stroke, and we could easily line the timing mark up on the crank.
We marked where the No. 1 plug wire attaches to the old cap, followed that, and marked the base of the distributor, and then we made a second mark on the engine itself. We also noted where the vacuum advance sits in relation to everything, although this is less critical. Then it was time to remove the distributor and old coil.
Installing the new distributor on the 360 requires some finesse because the DUI distributor has a larger body and it can be a tight fit, but not impossible. Fuel lines and the power steering pump all want to occupy the same location as the new distributor cap, wiring, and vacuum advance. Once you find the optimal location for the vacuum advance you’ll also want to get the rotor to point close to the mark you have on the engine for No. 1. This may mean trying different distributor gear to cam gear orientation or using a long screwdriver to rotate the oil pump so the distributor falls into the desired location completely.
Don’t forget the bushing at the bottom of the distributor, and adding some grease to the gear. That way the gear is protected until the engine builds oil pressure and it is bathed in lube. Also note that the higher-voltage spark of the DUI allows you to open up the spark plug gap to 0.055 inch for a hotter spark, which results in a more complete burn of the air-fuel mixture.
The cap of the DUI distributor has three wires that plug into the distributor and location for two other wires. One is tachometer and the other is 12-volt keyed power that you’ll run via 12-gauge wire from your ignition switch. It needs to see voltage both on start and run, so make sure you have the correct terminal. Using the old positive wire of the coil is not recommended since the wires may be too small.
With the engine still at TCD and the new rotor pointing towards your old marks, you can add the new cap and find the terminal lined up with the rotor, which will be your new No. 1 plug wire. From there, install your new plug wires in proper firing order. We upgraded to Performance Distributors’ LiveWire plug wires because of their insulation and coil wrapped stainless steel wire and magnetic core. The wires can resist damage from engine heat and exhaust headers while still transmitting your spark with very low resistance. Our only regret is getting bright yellow wires, as it quickly shows the grease and dirt of our old engine, and many other colors are available.
Once the distributor is installed and wired and the plug wires are installed, it’s time to set the timing. Remove the vacuum advance and cap off the hose so you don’t get a vacuum leak, and then adjust the timing as specified for your vehicle. Timing degrees are usually found on a decal in the engine bay. Loosen the distributor hold-down and turn it accordingly, then retighten. If you have any issues, double-check that your battery and charging system are up to spec because the DUI requires a healthy 12 volts.