1999-2004 Mustang GT Two-Valve Engine Bolt-Ons - Nice And Easy

Horse Sense: We know you'll probably read this story on Two-Valve power gains and say, "That's cool, but what's the deal with 5.0&SF's supercharged '02 Mustang project?" Fear not! While reports on our ProCharger-blown Two-Valve 'Stang will be continued soon, please understand the importance for us to address the basics from time to time. Remember, the 'Stang fraternity gains at least one new member each and every day. That's one of the reasons why we enjoy doing this so much

Lately, we've encountered Mustang enthusiasts-both neophytes and hardcore OGs-who firmly believe that the horsepower "buck" for stock 4.6 Two-Valve 'Stangs begins and ends with superchargers. These are the 'Stangbangers who pontificate on enthusiasts' Internet forums, singing high praises of boost. They quite often make performance claims about supercharged, stock 4.6s that go beyond the realm of possiblity, let alone believable.

Sure, a blower will wake up a stock 'Stang in relatively quick fashion, and in the past we've detailed the type of gains that can be achieved when you bolt a blower on a virgin modular. For this exercise, we're going to take a closer look at the cheaper alternatives for putting more zoom in your untouched Two-Valve. That's right, it's time to throw the originals at a stock, mod-motor Mustang.

Now, when we say "the originals," we're talking about the bolt-on parts that have become recognized as budget-friendly power producers throughtout the years. After-cat exhaust, throttle body and plenum, cold-air-induction system, underdrive pulleys, and a high-performance tune are a few examples of these.

This Two-Valve test comes to you on the heels of our recent Three-Valve, bolt-on report ("The Power of Three," Mar. '07, p. 134), when we installed cold-air and exhaust components as well as underdrive pulleys and an SCT tune on a stock '06 GT. The upgrades netted 30 additional rear-wheel horsepower on Gonzolo Topete's S197 at a cost of roughly $1,300. We've decided to keep the theme rolling and take a look at how the 4.6 in Ivan Lopez's '03 ragtop GT responds to similar treatment.

New Edge Mustang GTs are currently raising the popularity bar fairly high. Not only are '99-'04 'Stangs plentiful, many are still in the bone-stock trim that 'Stang-bangers lust for, for modifying, personal-izing, and upgrading. Another great quality is price. Although our test subject was purchased new from a dealer in 2003, we shopped around for today's ballpark price on a stock 'vert GT with 47,100 miles and found that $12,000-$15,000 can put you in the same car. Depending on mileage, some coupes can be had for less than $10,000.

The 4.6 upgrade parts we're using come from Accufab (throttle body/plenum), Cherry Bomb (Vortex after-cat exhaust), DiabloSport (Predator), JLT (ram-air intake system), and March Performance (underdrive pulleys). Saul "The Surgeon" Gutierrez will install each part, and we're immediately evaluating any gain or loss of horsepower or torque using the Dynapack Evolution 4000 chassis dyno at Extreme Automotive in Canoga Park, California.

The 'Stang is loaded on the twin-post hoist, and The Surgeon has disconnected the negative battery cable. Without further ado, let the bolting-on begin!

Using a reciprocating saw is quick and nearly the only way to extract a New Edge Mustang's factory tailpipes without losing your wits. With the tails gone, Saul unbolts the super-restrictive stock mufflers and prepares to install the Vortex kit.

Each section of the 2-inch tubing is mandrel-bent for spot-on fitment. Once Saul has the tailpipes installed over the axles, he uses the factory exhaust hangers to secure each one; the Vortex kit doesn't require any modification or relocation of OEM exhaust-mounting equipment.

Adding mufflers is an easy, slip-fit deal. Saul tucks one of the Cherry Bomb Pro cans (PN 7414; $55/each) in place. The aluminized-steel mufflers measure 19 inches from tip to tip, and feature 2-inch offsetting inlet and outlet openings. Cherry Bomb's unique, Wing Plate design allows exhaust to pass through while trapping high-frequency sound inside the mufflers. Wing plates in action are instantly detected when the engine is fired. The Cherry Bomb exhaust sounds almost stock at idle, and it only makes its presence known-and not in an annoying or obnoxious manner-under heavy throttle.

Once the exhaust is in place and the tailpipes are checked for straightness, Saul completes the installation by torquing clamp bolts down with Snap-on Tools' cordless impact wrench (PN CT4850; $499.95). This first bolt-on gave us a 4hp increase and an additional 8 lb-ft of rear-wheel torque. We think this modest gain could have been better had we swapped the OEM catalytic converters for a high-flow, X-shape cross-over. Amount of time required to bolt on: 2 hours and 30 minutes without a lift and with two people.

This Accufab 75mm throttle body and plenum package (PN F7546K; $469) is the first part of the induction segment of our upgrades. The all-inclusive kit is a direct swap with the factory combination.

"More air yields more power" is one of the main theories in high-performance. Accufab's big-mouth throttle body and upper plenum-designed with a smoother radius and a gargantuan opening into the intake manifold-helped prove the theory is correct as we saw 16 additional horsepower and 8 lb-ft of torque at the rear tires after bolting on the new induction pieces.

Amount of time required to bolt on: 30 minutes.

A free-flowing inlet tract is part two of the inlet-airflow equation. We selected JLT Performance's ram-air intake system (PN RAI-FMG-9604; $175) for Ivan's stocker. The ram-air kit includes everything you see in this photo (clamps, silicone reducers, removable S&B Powerstack filter) and a plastic heat shield that isn't shown. Unlike most CAI heat shields, JLT's isn't fully enclosed and thus blocks the filter from radiant heat only at low speed and idle. We ordered Gloss Black to match the color of our test 'Stang's exterior, but JLT's ram-air tubes can be ordered in almost any body color.

This huge, 4-inch JLT inlet is the heart and soul of JLT's ram-air intake kit. It's the largest air-inlet tube for Two-Valve engines that we know of, and since the pipe is made of plastic, it has a much greater resistance to heat-soak than similar metal inlets.

With the factory air-inlet system (air box/filter and tube) removed, Saul uses the mass air adapter to connect the 'Stang's original 80mm mass air to the ram-air tube.

The system also accepts much larger 90mm (Cobra/ Lightning) mass air meters.

The inclusion of this JLT Ram Air Intake system netted us four more rear-wheel horses and four extra lb-ft of torque. Keep in mind: torque is represented as a seat-of-the-pants/driving-experience sensation. With the gains we're recording from each bolt-on, we're fairly sure Ivan will immediately notice a difference in the way his 'Stang accelerates. Amount of time required to bolt on: 30 minutes.

The inclusion of this JLT Ram Air Intake system netted us four more rear-wheel horses and four extra lb-ft of torque. Keep in mind: torque is represented as a seat-of-the-pants/driving-experience sensation. With the gains we're recording from each bolt-on, we're fairly sure Ivan will immediately notice a difference in the way his 'Stang accelerates. Amount of time required to bolt on: 30 minutes.

Bolting on a three-piece, aluminum underdrive pulley system similar to this setup from March Performance (PN 1180; $209.94) is the ultimate method of reducing the amount of horsepower the engine gives up (also known as drag) as the serpentine belt turns the alter-nator and water pump. With underdrive pulleys, the belt-driven accessories run at a slower speed than the engine itself. The reduced drag brought on by slower accessory speed basically frees up horsepower and torque.

The six-rib, 5-inch, SFI 18.1-approved crankshaft damper on the right is markedly smaller than the stocker. The two parts interchange easily. Once the fan is removed, Saul uses a standard puller to dislodge the OEM balancer, an 18mm socket, and Snap-On's air impact gun (PN XT7100; $369.95) to install the new one; if using a standard torque wrench, secure the crank-pulley bolt with 60 lb-ft of torque. Saul recommends adding a dab of black silicone to the keyway inside the March pulley before installing it.

Our trio of underdrive pulleys netted six more ponies, and torque gained 6 lb-ft as well. Amount of time required to bolt on: 1 hour and 30 minutes.

DiabloSport's Predator handheld flash tuner (PN U7146; $439) rounds out our experiment. The Predator isn't a bolt-on component; it's actually a plug-and-play device loaded with three preprogrammed tunes for Two-Valve Mustang engines. Each tuning file is designed to optimize spark timing, and air/fuel ratio curves for maximum performance using 87-, 89- or 93-octane pump gas. The Predator is also used for controlling various PCM-driven drivetrain (engine/automatic transmission) functions and sensors, data recording, and engine-code diagnostics. It also serves as a conduit between a 'Stang's PCM and DiabloSport's Chipmaster Revolution tuning software that Saul uses for some of the more specialized tuning he does with power-adder-assisted modulars.

We used Predator's out-of-the-box Performance Tune (adds spark down low/reduces fuel at top end) for 93-octane fuel. California's petrol unfortunately lacks 2 octane points (91 is tops in Cali), but is considered high-performance nonetheless. Although we didn't have an air/fuel gauge to determine the engine's actual rich/lean status, we detected a hint of detonation at the top of our initial dyno hit. We felt the detonation unfairly stunted our max horsepower and torque results. Saul used Predator to dial up 8 percent more fuel, which seemed to do the trick (the tuner allows fuel and timing increases and reductions up to 10 percent). Ivan's upgraded 4.6 roared to the tune of 243.92 hp and 271.40 lb-ft of torque when all was said and done. Amount of time required to bolt on: 15 minutes.

While their collective price is on par with the amount you'll pay for an entry-level nitrous system, the cool thing about these basic bolt-ons is the fact that they make excellent naturally aspirated power and torque and don't require as much in terms of custom tuning, colder plugs, higher-octane fuel, or constant refills. Installing the parts can be done at home without any need for super-exotic tools-or a dyno. Sure, having a lift, a compressor, and air tools will make things easier, but all the parts we've detailed can be installed by anyone with the moxie to give it a try.