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Top Power and Mileage Mods You Can Do in a Day

Posted in How To: Tech Qa on April 2, 2016
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Engine power, performance, and mileage are things you never turn down more of, but not everybody’s 4x4 is a third or fourth vehicle that hangs around only to be used as a toy or play thing. For many it’s the way you get to work, drop the kids at school, or return your VHS tape at Blockbuster. For those people, any modification needs to be done, at the very least, over a weekend and preferably with no extra runs to the parts store (unless it’s within walking or biking distance). Here are some power mods we’ve made in the past that actually get you some return on your investment with a noticeable seat-of-the-pants increase in performance. As an added bonus, many will eke out a bit better fuel economy in the process because they make your engine more efficient.

Cold-Air Intake
The paper panel air filter that came in your vehicle is great for trapping particles, but they don’t really allow huge airflow. And the plastic ducting can be rife with harsh bends, baffles, and chambers designed more for low sound levels than maximum airflow. Adding a cold-air intake such as this unit for a ’12 Chevy Silverado with the 6.0L Vortex Max engine can add up to 2 mpg and provides a noticeable seat of the pants improvement in power from off-idle all the way to redline, thanks to a much better flowing filter element and free-flowing ducting. As a bonus, most of these systems add very little, if any, noise.

After-Cat Exhaust
Just like the air intake, the factory exhaust in your vehicle is designed primarily with low sound levels and ease of manufacturing in mind. Performance doesn’t really enter into the factory equation. Systems like this Flowmaster Hushpower system we installed on a ’12 Chevy Silverado 2500 uncorks the back end of the system and improves exhaust flow to help the cylinders scavenge the burned air/fuel mixture. Plus, it just sounds wickedly awesome. Empty cylinders on the exhaust stroke means more room for the fresh air/fuel mixture to enter the cylinder and, in turn, more power. The Flowmaster system is constructed of durable aluminized steel for an affordable price, nice mandrel bends and a fully welded muffler for performance, and applications to fit nearly any vehicle.
Flowmaster Mufflers

Adding headers can be a headache, but if you go with a quality stainless or heavy-gauge mild-steel application from a reputable manufacturer, then they can offer a great improvement in power and durability compared with cast-iron manifolds. Shown is a pair of Rusty’s Off Road stainless headers for a JK Wrangler 3.8L engine. These serve as a good example of what to consider in your header purchase: thick flanges that will resist warping, heat shielding where necessary (to keep plug wires and ignition components from burning), and quality welds with equal tube lengths for consistent cylinder scavenging. That said, not every application will benefit from headers and sometimes a good set of heavy cast manifolds are quieter and easier to deal with.
Rusty’s Off Road

Distributor Upgrade/Ignition Timing
If you’ve got an old-school distributor that relies on weights and springs to provide the advance curve, there’s most likely a ton of performance hiding right under your distributor cap. For starters, if you don’t know your base timing, you can use a vacuum gauge and advance the distributor with the engine idling and vacuum lines plugged until you measure your highest vacuum reading. Then, go into the advance curve. Kits are available for many factory and aftermarket distributors to tailor your timing curve, but for us, we’re always amazed at the ability of Performance Distributors to get the curve of its D.U.I. HEI distributors just about perfect with only a few questions over the phone. Even in back-to-back tests against a professionally recurved distributor on the dyno, the Performance Distributors unit out-performs all others we’ve tested to date.
Performance Distributors

Carburetor Swap
If you have a two-barrel carburetor, you can often use a two-to-four-barrel adapter like those from Trans-Dapt Performance to mate a square- or spread-bore four-barrel to your two-barrel manifold. It’s not ideal, but you’ll still be able to enjoy some of the benefits of a four-barrel without swapping intakes. We love junkyard Q-Jets, but they’re getting scarce. One company still manufacturing excellent off-road carburetors is Holley, with its Truck Avenger line of off-road–bred carburetors. Available in 470, 670, and 770 cfm applications, the Truck Avenger covers everything from six-cylinders all the way up to big-block applications. Just don’t go too big. Most small-block engines will respond well with a 670 cfm unit. Save the 770 cfm job for the big-blocks and really nasty small-blocks.
Trans-Dapt Performance

Intake Manifold
Upgrading from your cast-iron log of a factory intake manifold to a high-performance aluminum intake manifold can offer a night-and-day difference in performance. Many manufacturers offer many types for a variety of applications, but in our minds, none successfully cover emissions and non-emissions applications as well as Edelbrock. The manifolds are made right here in the USA and, in our opinion, are of the highest quality and offer stellar performance. Several different varieties are available, but you simply can’t go wrong with either a Performer or (for slightly more performance-oriented builds) a Performer RPM, no matter what you’re building.

Ignition Coil/Plug Gap
Most modern vehicles feature either coil-on-plug ignition systems in which the coil is (duh) right on the plug or attached to the valve cover and connected to the plug via a short wire. In any case, Performance Distributors has developed a super-high-output coil for these applications it calls its Sultans of Spark. The high-output coils allow the plugs to be opened up to 0.065 inch for a complete burn of the air/fuel charge, no matter what load or rpm level. The plug wires are super-low resistance beauties with durable silicone insulation and a high-temp braided heat shield. They’re simply the best. We’ve been testing this system in a ’12 Chevy Silverado with a 6.0L Vortec Maxx engine, and after 20,000 miles we’ve seen a consistent mileage increase and bump in power.
Performance Distributors

Fuel Injection
For off-road performance that translates onto the street, it’s hard to beat a fuel-injection conversion system. There are a lot of fancy MPI systems out there, but for all our experience, one of the simplest and best working units we’ve ever had was the self-learning Powerjection III system by Professional Products. We simply installed the system in place of our four-barrel carb (we used Professional Products’ optional fuel pump and line kit), answered a few quick questions on our laptop, and then drove the vehicle. It measures variables from the O2 and other sensors to quickly and accurately tune the system for your particular vehicle. It’s that simple.
Professional Products

Throttle Body
In modern fuel-injected engines, the throttle body can be a potential choke point in the intake charge. Taking a Jeep 4.0L as an example, the factory throttle body (left) necks down to 60 mm. Many aftermarket companies, like BBK, offer throttle bodies without the taper with a larger diameter opening. Going too large on the throttle body can actually reduce the intake charge velocity and make the engine lazy at lower rpms, so most are in the neighborhood of 62mm, which is plenty for a factory Jeep 4.0L with a few accessories like a header, cold-air intake, and after-cat exhaust.
BBK Performance

It’s especially true if you’re driving a modern diesel pickup but even gasoline-powered vehicles can benefit greatly from a good aftermarket tuner/programmer to increase power, mileage, change shift points, diagnose trouble codes, and (especially nowadays) provide a dashboard-gauge view of virtually any factory sensor in the vehicle. We’ve been running a DiabloSport Trinity T1000 tuner in a ’12 Chevy Silverado 2500. We used the unit to raise the transmission shift points up to 6,000 rpm, employ the gauge dash when under way to monitor things like tranny temp while towing, oil pressure, and water temp, as well use any of many other functions it offers like data logging, DTC reader, and more. In Performance mode it makes the truck an absolute beast, and in economy mode, we can eke out up to 3 mpg more from our rig in normal driving and 2 mph when towing a 12,000-pound trailer. That’s performance that pays for itself!

Nitrous Oxide
It may not be right for every application, and you sure aren’t gonna get better mileage with it. But one of the fastest and easiest ways to add oodles of power to any engine is with a nitrous oxide system. We’ve used many, and the Powershot system from NOS was simple and brutally effective. A wet-jet system, the Powershot uses a nitrous and fuel jet upstream of the throttle body in a fuel-injected vehicle to add the appropriate levels fuel and nitrous to make around 90 hp on a six-cylinder and 125 hp on an eight cylinder. Of course, you can change jetting for more or less power as desired.

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