Words and photos by Bryan Irons
Ever notice that certain phrases in online For Sale ads seem to be the epitome of disaster? You can practically smell your money burning as you scan an ad for a project rig that calmly recites what you know are toxic proclamations. Some of our favourites are simple ones like “minor rust”, “unknown mileage” and “easily fixed”. A headline with capital letters exclaiming “MECHANICS SPECIAL” sends cold chills to the ends of our fingers along with quips like “requires inspection”. If the seller throws in some sage advice like “only requires $20 part to be a runner” we know that unless the vehicle is free and delivered, this order is a money pit with a side of “angry better half”.
We’re not here to let you that we’re immune to these disastrous lines, we’re here to tell you that these are the ones we can easily pick out. We personally have fallen victim to the words “rare” and “needs new home” often enough that the resulting collection of lawn ornaments was deemed “unacceptable” to the neighbourhood association. Our buddy Darren seems to fall prey to the phrase “ran when parked”, and he falls hard.
His most recent ‘trucktastrophy’ is an eighty-something-er-other Jeep CJ-7 rust bucket that needed rescuing before it was recycled. Maybe he felt sorry for the old beater, but as soon as we heard that the old 258 ci inline 6 cylinder was last heard running a decade back, we knew that no amount of wishing or praying was going to get the old lump running without some serious planning and help.
The basics to getting an old beater to run are simple and we categorize these basics into five areas; Air, Fuel, and Spark are the common ones, but without Confinement and Timing, you just have a mess. Possibly a hot, gasoline soaked, burning mess.
Air and Confinement (or compression) work hand in hand and the easiest way to determine if air is getting into the cylinders and Confined is a with a compression test. With a motor like Darren’s 258 ci Jeep hulk that has sat open to the elements, it is best to pull all the spark plugs and put a few cc’s of automatic transmission fluid (ATF) into each cylinder to keep the piston rigs from grinding against the cylinder walls. The longer you let it sit, the better. Darren had let the ATF soak for a few days and then turned the motor over by hand to make sure everything was nice and loose. After this, the motors starter can be used to turn the engine over AFTER you do an oil change. A basic compression test setup can be purchased for very little money, or even rented from many major automotive parts sellers. We seem to be attracted to garbage motors, so we keep one on hand. Follow the directions and ensure that air is entering the cylinders, compressing, and leaving out the exhaust. We’re not looking for performance numbers here, just enough compression to burn fuel.
With the old six-banger showing that it had some life left in it, we moved on to the Fuel aspect of our adventure. The original Carter BBD electronically controlled carburetor remained atop the old engine, but we were pretty sure it contained more bad fuel and blocked passages then we were willing to deal with. Besides, the BBD series of scrap metal carry with them the reliability of a political promise. Plenty of fancy EFI units can be adapted to the inline 6, and even a few units such as Holley Sniper AMC 258 system designed specifically for the old Jeep come complete with an entire high-pressure fuel system and all the components needed to step the old motor into the 21st century. For now, we used a Motorcraft 2100 series carburetor. Once we know the motor is a keeper, we’ll look into the Holley unit. The Motorcraft swap is extremely easy and reliable, and the parts can be salvaged from many an old Ford pickup truck languishing in a junkyard near you.
While dealing with the fuel system, don’t forget to drain the old fuel out of the system and attempt to blow out the fuel lines as well. Stale fuel and the varnish it leaves behind can stop your plans of a smooth running engine in a heartbeat. For low pressure fuel systems in carbureted vehicles, we like using the cheapy clear fuel filters so we can see what we’re feeding the engine. We’re not sure it does anything or just appeases the motor Gods, but for an initial fire up, we like using the highest octane fuel we can score at the pumps, even if it’s just a jerry can worth.
Spark was our last hurdle to make the old motor a runner. A new set of spark plugs is a no brainer at this point and a good way to see how well the motor is running. The original distributor is a factory mish-mash of Ford and Dodge leftovers that AMC managed to scrounge together to get their vehicles running for cheap. The beautiful, resonating tone of it hitting the bottom of the scrap bin can be described as righteous as the ring of a church bell on a sunny Sunday morning. In its place, a Davis Unified Ignition (DUI) all-in-one distributor now sits.
General Motors derived HEI (High Energy Ignition) distributors can be found in many vehicles from the 70’s all the way up to the early 90’s and range from 4-cylinder fuel misers up to behemoth 450+ cubic inch monster V8’s. Their reliability and simplicity are that of legend and DUI adapted the design to many other engine manufactures… such as Jeep. The units come as a single drop in replacement that only require power from a single 12V switched ignition and a vacuum source to operate. The rest is all done internally with easy to source, over the counter parts. No coils to mount, or ignition modules to wire, just one switched source and it’s ready to run. Summit Racing sells DUI distributors, and Darren ordered this one though them, but if you have heavily modified engine, we recommend that you call DUI directly with your specs in hand. The experts there can custom curve the distributor advance timing features to your specific engine, and at no extra cost, but it may take some extra time to get to you. We had no idea what the internals of this engine consisted of, so we didn’t feel the need to order directly from DUI.
While Darren was ordering parts from Summit Racing, he scooped a set of DUI Live Wires ignition wires as well. The 8mm units are designed to work with the HEI style distributor cap that the DUI distributor comes with, and the ends are cut and crimped to length to work perfectly with the 258. The heat shielding and woven covering for added protection is a nice bonus. Between part swapping, fluid changes and test measurements taken, it was time to cross fingers, make sacrifices, praise overlords and use our birthday wish as we turned the key…
DOH! We forgot about timing. When replacing a distributor, it’s best to try and ensure that the #1 spark plug lead and the rotor position match the old setup when restarting the engine but some adjustment on the fly to get the motor to run may be required. After a few choice words and hollow threats, the old motor coughed and belched itself to life. VICTORY At LAST! We drug out our trusty Summit Racing Timing light and set our base timing to DUI’s recommended 12 degrees advance and proceeded to tinker with the new Motorcraft. Honestly, we never heard this old lump run in the past, but from what we know now, we see the old straight six and its new lease on life lasting long into the future… provided another lost soul with a rusty heart doesn’t distract Darren.
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Any fuel filter with surface rust is a prime candidate for replacement.
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Darren had previously drained the tank of whatever non-flammable gunk was left in the tank. Be warned; you can’t “unsmell” rotten fuel.
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Moving to the other end of the fuel system led us to the carburetor, or at least its Motorcraft 2100 replacement. This is a very common swap on these motors as the carb is plentiful and easy to work on… not to mention reliable!
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The DUI distributor comes complete from oil pump drive to cap (missing in the pic), and you can pick from a plethora of colors… even camouflage… really!
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With the new distributor in place, the included hold down clamp can be put in place. No need to cinch it down just yet, let’s get the motor up and running first!
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The cap and high voltage coil can be placed on the DUI distributor. Because of the higher output voltage, the spark plug gap can be opened up to allow for a larger spark. The DUI instructions tell you how large.
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Our new Live Wires spark plug wires can be put in place. Each lead is numbered for easy routing and come with wire separators. Make sure new spark plugs are on the end of those fancy new wires!
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The final connections include the vacuum advance to the carburetor and a 12V switched ignition source. For us, all the hard work paid off and the old 4.2L Jeep motor sparked to life!