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Techline: Your Top 4x4 and Off-Road Tech Questions Answered Here

Posted in How To: Tech Qa on September 18, 2019
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JK Long Arm
My friend has a '17 Jeep Wrangler Rubicon Unlimited. He's looking to move up to 35-inch tires and asked my opinion. I told him to look at long-arm kits as they improved the ride on my '05 LJ, but his shop told him that a short-arm kit will get him a better ride than a long-arm kit. I know it's only a 2.5-inch lift, but does that jive with you? It sounds suspicious to me.
Darek Connole
Via facebook.com/JohnCappa4x4

It's always interesting when a new-model Jeep Wrangler comes out. Enthusiasts and manufacturers alike initially tend to grasp at the known and develop the same products that were successful on the previous generation of Wrangler. I've been fortunate enough to see this process occur three times for the Wrangler now. Sometimes these ideas work, and sometimes the products are completely unnecessary because of the differences of the vehicles. Long-arm suspension is one of those products. The '97-'06 Jeep Wrangler came with incredibly short control arms. Pretty much any lift kit more than an inch or two put the control arms at undesirable angles. This offered poor handing and a degraded ride. In answer to this, the aftermarket developed long-arm suspension systems for the TJ and TJ Unlimited (LJ) Wranglers. The longer suspension control arms improved the ride and handling of lifted '97-'06 Wranglers.

Fast-forward to '07 with the introduction of the Jeep JK Wrangler: The manufacturers were quick to create long-arm lift kits for the new Jeep. Unfortunately, there were several features on the new Jeep that made aftermarket long-arm lift kits less necessary. The JK came with significantly longer control arms than the TJ/LJ. The arms also sat flatter at stock ride height. But more importantly, the JK wheel openings were larger than what was found on the TJ and LJ, allowing for bigger tires with no lift. Smaller lifts on the JK offered enough clearance to easily fit 35-inch tires, which keeps the control arms at tolerable angles. Ride and handling are not adversely affected as much as with the bigger lifts required to fit the same tires on a TJ/LJ. Of course, the aftermarket had another solution for the TJ/LJ in the form of long-arm lift kits with a low center of gravity and raised fenders, but these didn't significantly come into play until late in the TJ/LJ production cycle.

When fitting 35-inch tires on a JK, you can get away with a smaller lift of 2.5 inches or even less if done properly. The control arm angles will not change significantly, so an aftermarket long-arm suspension system really isn't necessary. Would a long-arm kit ride smoother than using the stock-length control arms? Sure, but it may not be a significant enough difference to justify the cost and complexity on a JK. The JK long-arm kits are generally reserved for bigger lifts that provide clearance for 37-inch tires and larger.

Fan of Wiring
I'm running Ford Contour dual electric fans on my LS-swapped CJ-7 and I just burned up the wiring for the second time in six years. I'm using two Bosch 40-amp relays. Does anyone make or offer a do-it-yourself relay harness that uses heavy 10 gauge wire and is waterproof? The harness plugs I am using I found on eBay years ago and they only use 12 gauge wire for the feeds and 16 gauge for the triggers. I'm looking for something that is heavier and better quality.
Phillip Harader
Via facebook.com/JohnCappa4x4

Electric fans are great for moving massive amounts of air at slower speeds and at lower engine rpm. This is a huge advantage for a 4x4 used on the trail. The disadvantage of electric fans is that they can sap quite a bit of power and may require a high-amp alternator. The amperage that an electric fan pulls can generate a lot of heat, especially if there is a bottleneck in the system, such as wires that are too small, corroded connectors, or even connectors and fuses that are too small.

The twin 40-amp relays you are using should be plenty for most dual electric fan systems. You may need to investigate where the meltdown is starting. It's been my experience that electric fan wiring meltdowns often begin at the fuses and fuse holders. Smallish 40-amp ATO-, ATC-, and Mini-type fuses often have difficulty shedding the heat generated by the power draw of large electric fans. The melting can start at the fuse holder and lead to other electrical issues and even underhood fires. The much larger Maxi fuses and associated connecters can shed heat a little better, but I have still seen these melt and deform under the draw of a powerful electric engine cooling fan.

Companies such as Be Cool (becool.com), Painless Performance (painlessperformance.com), Spal (spalusa.com), and many others offer quality electric fan wiring harnesses with 40-amp relays, but I think you may need to look a little further. Keep in mind that sometimes older electric fans become less efficient when worn out. This can cause increased impedance and heat in the wiring harness, which may lead to the harness melting or catching fire. You could try replacing the fans or simply bump up the size of the wiring and other electrical components. One option is to switch dual 40-amp automatic circuit breakers with ring terminals along with your 40-amp relays. You could also consider making the switch to a single continuous-duty 85-amp or 100-amp solenoid and circuit breaker system. Look for solenoids and circuit breakers with ring terminals on the feeds rather than plugs, which can more easily come loose or corrode, leading to electrical resistance and heat. Companies such as Bussmann (cooperindustries.com), West Marine (westmarine.com), and Summit Racing (summitracing.com) offer waterproof high-amp circuit breakers and continuous-duty solenoids that would work perfect for your wiring project.

Carb Cough
I have a '46 Jeep CJ-2A that is my trailer queen. It features a 225ci Buick odd-fire V-6 engine with a GM two-barrel carburetor. The engine runs great except for on long, rough, steep inclines, where I believe the fuel is running out of the bowl and floods the engine. Is there any fix for this sort of problem short of fuel injection? Is there a mod for this carburetor or a different carburetor I can use? Thank you for your time in reviewing my problem.
Alan J. Haynes Sr.
Reno, NV

You have clearly encountered the age-old issue of carburetors coughing off-road. The problem is that your carburetor relies on gravity to maintain proper float bowl fuel levels. As you introduce off-road angles and bumps into the equation, the carburetor floats react to the sloshing fuel by either staying closed when they should be open or opening when they should be closed. This temporarily alters the float level away from ideal. The result is over- or under-fueling, depending on the application. Sometimes the float bowls can be so overfilled that they splash out of the vent tube and down the throat of the carburetor, causing an overly rich condition. Some of the more popular carburetors have aftermarket spring-loaded seats available, which will help control float levels at odd angles. If you are experiencing an overly rich condition on hills and bumps, a popular low-buck method of curing the carb cough is to lower the float levels so fuel doesn't spill down the carb throat. This can work if you don't need the high-rpm capacity of the carburetor. If you regularly rev the V-6 with low float bowl levels, you could cause a lean condition and possible engine damage. Another option is to extend the float bowl vent tube into the air cleaner to reduce fuel slosh on hills.

Ultimately, the best (and unfortunately the most expensive) solution is to convert to fuel injection. A pressurized fuel injection system eliminates all of the carburetor problems associated with off-road angles. Companies such as Howell EFI (howellefi.com) offer throttle-body fuel injection kits for many different engines, including a kit specifically for your Buick 225ci V-6. If you plan on sticking with the Buick engine for a while, it might be worth making the conversion.

AMC Eagle Upgrades
I have an AMC Eagle. It's my $5 raffle car that I drive daily. It has an anemic 4.2L with the infamous two-barrel BBD carburetor. Eventually, either that carb or the rudimentary electronics feeding it are going to give up. They all tend to. The car only has 115,000 miles on it and it runs OK. It doesn't smoke, but it uses the usual amount of oil for a 36-year-old AMC engine via valve cover leakage. The biggest downfall of the car is spending time in the slow lane with my hazard lights on anytime I come to a grade on the highway.

What are your thoughts concerning 4.0L and 4.2L engines. Before I start, yes, I know a fuel-injected 4.0L is the best way to go. But my starting point has none of the electronics for that. And while I've seen many write-ups on how to swap in a 4.0L with all the electronics, I want to keep it simple. I want to either stay with the 4.2L and wake it up a little or go with the 4.0L and not have to deal with all the rewiring of my car.

There are a few options to get me where I want to be. I could go the simple route and do a Nutter Bypass, swap the carb with a Weber, a Motorcraft 2150, or one of the many throttle-body injection systems out there, and be done with it.

The Weber carb seems to have the advantage when it comes to the carb route. I have a friend that did the Nutter Bypass on his YJ and installed a Weber carb. It was an eye opening transformation from the old BBD and I swear half his engine compartment was emptied of all the excess pieces and parts he was able to remove.

The TBI route appears to be a good way to go too, but with all the options out there, which is best? Some systems require pulling out the dash to situate the ECM and a lot of wiring. Others, such as the Holley Sniper BBD replacement appear to be a simple install without having to do too much disassembly. The downside of the TBI route is that those things are pricey!

Of course, there was always the option of the Chrysler MPFI kit made for the 4.2L Jeeps. I don't think they make them anymore. I've heard of a few guys that adapted these to their Eagles with great results. Of course, lots of wiring and money involved. As I said, I don't think this is an option anymore.

Then, there are other routes to take with the 4.2L. Could I add the 4.0L head to my 4.2L? I've read lots where this is a good way to go, but which head to use? Which intake and exhaust manifold should I use? As I said, I'm trying to keep this simple and cheap but get a little more power out of the car.

I could add an HEI distributor. My car is mostly stock. I really don't want this huge HEI cap stuck on the side of my motor screaming at everyone that looks under my hood. And there are so many different brands out there, who knows which the better of the bunch is. I keep looking for a small-cap HEI for the AMC engine. The OEM distributor currently works fine, and I really don't see much of an advantage of the HEI other than I can get rid of a few more parts, like the external ignition module and mounts on the inner wheelwell. My ignition is still original, so there is no telling when that'll fail and I'll have to get a foreign-made replacement and replace it every few years. No, they don't make them like they used to. And lastly, there's the stealth or junkyard HEI. It's an interesting way to get rid of the factory ignition box.

The next idea would be a complete swap out of the 4.2L for a Jeep 4.0L. Nice engine, mostly a direct bolt in, but if I take the route of a full swap with the factory fuel injection, that's a lot of wiring and modifications to do. Also, I'd have to add a crank position sensor and a few other parts if I plan on keeping my factory, recently rebuilt, 998 transmission or just replace the entire drivetrain with an engine, transmission and transfer case out of a Jeep. Again, I've went way past my keep it simple plan.

Maybe I could do a 4.0L swap, but convert it to a carburetor or TBI. The problem is, very little is written up on this. What distributor would I use for this and what else will I need to do? Would I need to use a different intake to adapt a carburetor or TBI? Which exhaust manifold? I would love to see an article somewhere that covers changing a fuel-injected 4.0L to a carburetor or TBI. Thanks for all of your thoughts.
Rich Comer
Via email

You've certainly covered the bases of all of your possible AMC Eagle engine upgrades. Some make good sense and some would require a boatload of money to perform, while others, such as converting a 4.0L to a carb or TBI, don't make much sense and are not really a cost-effective route to go. I get the feeling that you'd like to stick with the best bang for the buck in performance and reliability. With that in mind, I would recommend you improve on the ignition and fuel delivery. Remove the factory ignition system and replace it with a Performance Distributors (performancedistributors.com) DUI ignition. These distributors are tuned to your application and will provide a hotter spark than stock. You'll be able to open up the plug gap and more efficiently burn the fuel introduced into the cylinders. The engine will make more power and burn cleaner. You can order the DUI ignition with a black cap, making it less obvious under the hood, although I'm not completely sure why this would be an issue for you if you are considering something like a 4.0L swap, which would include lots of modern wizardry under the hood.

Next, scrap the problematic factory carburetor. The Weber (redlineweber.com) carb is a real good performer, but with it you will see a significant drop in fuel economy. The TBI is probably a better route for you. You'll see improved off-road performance and better fuel economy than you would get with the Weber carb. The Mopar MPI kits are no longer available. Regardless, Mopar MPI performance and fuel economy is on par with the available aftermarket TBI kits. The Mopar MPI kit was simply an expensive and complex solution to the problem. Howell EFI (howellefi.com) offers fairly priced, emissions-legal TBI kits for the Jeep 4.2L inline-six engines. The Holley (holley.com) Sniper EFI is also a good option.

These ignition and intake mods will wake up your 4.2L without totally breaking the bank or requiring massive amounts of work on your part. Even shade-tree mechanics should be able to easily perform the two modifications over a lazy weekend.

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