KJ Jones Brand Manager, 5.0 Mustang & Super Fords
April 15, 2014

Horse Sense

While you may not be familiar with Tony Napolitano, owner of the 2013 Boss 302 that stars in this tech report, we’re willing to bet you’ve seen footage of Tony’s other Pony, aka Grey Mare. Find some footage at YouTube under “AV Boys Grey Mare.” The mega-rpm, naturally aspirated (331ci) 1989 Mustang LX has built quite a reputation for itself through hard, tire-yanking launches on the streets of Southern California.

As we fast approach the beginning of a new era for Mustang, our favorite ride’s future is bright—especially once the aftermarket starts developing parts for modifying ’15 ’Stangs. Despite the availability of a titilating EcoBoost engine option, the Coyote will reign as the Mustang GT’s premiere powerplant.

It’s a safe bet that every ’Stangbanger in the game is familiar with the Four-Valve Coyote 5.0-liter, and the ’11-’14 Pony it motivates. To put it simply, this engine is a beast in its naturally aspirated state, and really becomes a monster when power adders are implemented. However, while the ‘11-’14 Coyote steals most of the headlines, its cousin, the Roadrunner found between the front fenders of ’12-’13 Boss 302s, is the limited-edition mill that takes the modern-day 5.0 to another dimension.

Bringing back the mystique of the Boss 302 of the late ’60s-early ’70s was the mission of this car and its special engine. Like the original, the modern Boss is basically a street-legal version of a road-race-caliber Mustang, highlighted by a tauter suspension package and the aforementioned Roadrunner; a higher revving, more powerful version of the new 5.0 that features a beefier rotating setup, ported head castings, and a short-runner intake manifold. Superior breathing, promoted by the intake manifold and heads, is the trait that really positions the ’12-’13 Boss 302 as the baddest naturally aspirated ‘Stang to come off Ford’s assembly line in a long time.

Moving intake and exhaust air in the most efficient manner is the name of the game when it comes to engine performance, and the basic bolt-on pieces fully confirm this credo, especially for modern 5.0-liter engines. When it comes to Roadrunners, however, more performance is definitely available with more aggressive mods.

Of course, the knee-jerk reaction to go beyond the basics is a supercharger, which automatically makes any late-model ’Stang much hotter. However, when you think about a Boss and its lineage, there is a lot to be said about hopping one up without using forced air.

Eddie Rios and Tony Napolitano tore the top off the the brand-new, engine in Tony’s ’13 Boss 302. While a photo of this type of disassembly usually marks the start of a supercharger installation, we’re taking a different path with Tony’s Boss by replacing the intake manifold, air-induction hardware, exhaust, and camshafts in a quest for more NA horsepower.

Based on the Roadrunner engine’s makeup and the aforementioned factory-installed hardware that gives it more lung than a Coyote, swapping stock camshafts, intake manifold/throttle-body, air-induction and exhaust manifolds with their improved, aftermarket counterparts is the most-logical modification for ’12-’13 Boss 302s, and the package we’ve assembled to do so emphasizes this.

Southern California’s Tony Napolitano is a firm believer in doing things the natural way. As such, Tony agreed to let us use his bone-stock ’13 Boss for our upgrade project. We added Dynatech’s Boss-specific, long-tube headers (PN 722-94310) and catted mid-pipe (PN 722-94320), plus a collection of next-level induction goodies, highlighted by a Ford Racing Performance Parts Cobra Jet intake manifold (PN M-9424-M50CJ), throttle body (M-9926-CJ65) and 13mm-lift Boss 302 camshafts (PN M-6550-M50BINT and M-6550-M50BEXH).

This combination elevates naturally aspirated ’12-’13 Boss’ cred to ultimate levels. “We see so many new Mustangs out there with forced air,” Eddie Rios of Addiction Motorsports says. “The Boss 302 is already a badass ride that outshines GTs eight ways to Sunday. To make 60-70 more horsepower with a new intake, cams, headers, and tuning is awesome, because the cost is lower than that of a forced-air, power-adder system.”

With Tony’s assistance, Eddie performed the surgery for this project and dialed in the steam with a custom PCM calibration after all the parts were installed. The accompanying photos and captions highlight the process, and dyno results confirm the effect ultimate naturally aspirated upgrades have on a stock Boss 302.

1. This is Tony’s bone-stock Boss engine before surgery. Rated at 444 horsepower and 380 lb-ft of torque at the crankshaft, the 5.0-liter powerplant, dubbed Roadrunner by Ford engineers, because it’s faster than a Coyote, baselined at 391.23 horsepower and 351.72 lb-ft on the Dynojet chassis dyno at Addiction Motorsports.

2. Dynatech’s SuperMaxx long-tube headers are first on our replacement list. Using a transmission jack (and pole jacks to support the engine), Eddie and Tony remove the entire front subframe from the Boss 302, which creates ample room for removing stock exhaust manifolds and installing the Dynatech tubes.

3. The Dynatech header system (PN 722-94310 and 722-94320) features full-length, stainless-steel, 17⁄8-inch primary tubes, and 3-inch collectors that mate with either of the Boss-specific, X-shaped crossovers (catted or non-catted) offered by Dynatech. When compared with the factory exhaust manifold, it’s not hard to see the improved efficiency. With their straighter, larger diameter tubes, the Dynatech headers send gasses almost directly from the heads to the collectors, and ultimately through the system and out of the ’Stang.

4. As a big fan of naturally aspirated performance, Tony is a strong advocate of the lightweight concept—especially when it comes to the drivetrain’s rotating mass. While the starter was removed for the header install, we couldn’t help noticing a sneaky change Tony made to lighten things up. The Boss 302’s stock, steel flywheel was replaced with an aluminum ’wheel, to help hasten the engine’s rev speed. While this might be a standard change with a clutch upgrade, Tony actually had a buddy machine the aluminum flywheel to work with the stock clutch assembly. We think this mod ultimately will go hand in hand with the changes we’re making in this effort.

5. Eddie bolts the new headers onto the engine. While working from below really is the only/best way to go about installing long-tubes on an S197, the procedure is still lengthy nonetheless.

6. Here’s a look at the headers installed. Fitment is very clean, and the driver-side tubes don’t present any conflict or problem with the Boss’s steering linkage.

7. In an effort to corral the exhaust’s noise output, we chose Dynatech’s Power Cats—high-flow catalytic converters (left)—as opposed to eliminating converters altogether. The upgrade catalytics are more compact than the OEM pieces, and much less restrictive.

8a-b. As you see in this photo, the stock Boss 302 H-pipe (top) features flanges for unique side-exit exhaust tubes. The flanges also are incorporated in the Dynatech X-shaped midpipe to retain the sidepipes without any modifications. We dig Dynatech’s four-bolt collector flanges. Most headers are designed with two-bolt collectors. The addition of two extra bolts guarantees the X-pipe-to-collector union will be solid and leak free. The system uses 3-inch, stainless-steel band clamps to secure the cats to the X.

9a-b. With headers installed, Eddie moves on to exchanging the camshafts on Tony’s ’13 Boss 302. Naturally, cam covers, the intake manifold/throttle body/air-induction system, and also the timing cover are among the engine pieces that must be removed for this procedure.

10. Clean is crucial when working with internal engine parts. Clean is also Tony’s way of life, to the point of obsession. Ensuring the new cams were free of any packaging debris or other dirt was left to the Cleanmiester, who did a wonderful job prepping all four bumpsticks.

11. We’re swapping the stock cams with Ford Racing Performance Parts’ Boss 302 upgrade camshafts (PN M-6550-M50BEXH and M-6550-M50BINT). The billet 13mm intake and exhaust cams have more lift (1mm intake, 2mm exhaust) and provide more duration (290 versus 263 exhaust, and 263 versus 260 intake) than the OEM sticks, and can be installed without requiring removal of the cylinder heads. The exhaust cams and their massive duration, when considered with the Dynatech long-tube headers, are the difference makers in this segment of our Boss 302 upgrade. In this example, notice the cam on the right, which does not have a QR code. In addition to the factory cams not being billet, the QR code (or the absence of one) is the best way to identify a Ford Racing cam.