When Ford unleashed the BOSS 302 nameplate on the Mustang world in 2012 they created the ultimate driving Mustang. With improved horsepower and a chassis capable of putting much more expensive cars to shame, the BOSS was one of the best engineering exercises in Mustang history.
Most BOSS owners are like any other enthusiasts, they plan to drive their Mustangs hard and are looking for the best bang for the buck with the best engineered upgrades available to them. With that in mind, Ford Racing created several upgrades for the BOSS engine that build upon the strengths of that car while adhering to strict Ford production standards.
We recently had a chance to follow along as one owner sought to create the ultimate naturally aspirated BOSS. The results from a few bolt-on parts and a new tune are impressive, to say the least.
Breathing Deeper
You’ve no doubt heard the comparison of an internal combustion engine to an air pump. The more air you can inhale and exhale, the more efficient and powerful the pump becomes. Part of what gave the BOSS its high-revving ability and more horsepower was its unique intake manifold. This high-rise, long-runner piece has become a favorite of enthusiasts and flows more air than the standard 5.0 intake found on the Mustang GT.
The BOSS intake is not without some drawbacks. According to Ford Racing’s Dave Born, this intake still had to meet many production standards, like packaging constraints for the assembly line. As a result the BOSS intake had to make a few compromises before it ever made it down the assembly line. That doesn’t mean it’s not a good intake, but sometimes you can do better when you don’t have to produce a part for mass consumption. That’s where the Ford Racing Cobra Jet intake manifold, part number M-9424-M50CJ, picks up what the BOSS had to leave behind.
“With the Cobra Jet intake we’re dealing with enthusiasts who are bolting this part on at home or in a shop environment. That solves several of the packaging constraints of the BOSS manifold,” says Born. “This lower volume intake allows us more flexibility with the design.”
The Cobra Jet manifold is an evolutionary product that began with engineers installing a larger oval or dual-bore style throttle body inlet onto a BOSS intake for testing. From there the project continued to evolve with engineers seeking to find other ways to improve on the airflow of the BOSS.
The Cobra Jet manifold features larger intake runners and is devoid of the interference in the bell mouth on the rear runners for cylinders four and eight that were mandatory for the production line BOSS piece. There’s also no interference from the injector pockets with the intake runners on the Cobra Jet intake.
With the Cobra Jet intake we’re dealing with enthusiasts who are bolting this part on at home or in a shop environment. That solves several of the packaging constraints of the BOSS manifold. -Dave Born, Ford Racing
Bringing the air into that Cobra Jet intake is a Ford Racing 65 mm Cobra Jet Billet Aluminum Throttle Body, part number M-9926-CJ65. Machined from billet aluminum and featuring big 65 mm twin inlets, this throttle body is capable of inhaling a massive 1,517 cfm. It’s ready to bolt on without the need to transfer the factory electronics. The unit is calibrated for stock idle air flow characteristics and also uses stock throttle body gearing to prevent bind or wear.
That throttle body breathes through a Ford Racing Cobra Jet Cold Air Intake Kit, part number M-9603-M50CJ. This air intake has a huge 102 mm air inlet diameter to feed that hungry throttle body. It also uses a high flow air filter and molded plastic housing to supply that filter with plenty of fresh air.
Putting The Bump In The Thump
Upgrading a BOSS to be the ultimate naturally aspirated example wouldn’t be complete without revisiting the camshafts. To that end Ford Racing supplied us with a set of intake and exhaust cams to liven up things in the horsepower department. Both of these cams measure 13 mm gross lift with 263 degrees duration on the intake cams and 290 degrees duration on the exhaust. These cams are available from Ford Racing, the intake cam set is part number M-6550-M50BINT, and the exhaust cam set is part number M-6550-M50BEXH.
The cams underwent the same engineering standards, and were developed by the same team as the original BOSS components. -Dave Born, Ford Racing
According to Born, the exhaust cams were developed with increasing BOSS performance in mind. These cams also underwent the same stringent development process as the intake cams. Engineered to maximize naturally aspirated BOSS engine output without the need for additional internal modifications these cams unleash the horsepower within the BOSS’s Roadrunner engine.
Full Phase Retention
The Ford Racing camshafts allow for full retention of the cam phaser driven Ti-VCT system. What this means for enthusiasts is that there are no limiters being installed in the cam phasers. On the street and the track this translates to OEM level response down low and the engine’s ability to then go up high bridging the gap between a high winding race engine and a torquey street machine.
Born tells us that like the intake cams the exhaust cams were designed to make full use of the stock Ti-VCT cam phaser system. This means that these cams don’t give up low or mid-range performance in favor of higher peak numbers. These cams also don’t require the use of limiters which restrict the operation of the phasers.
“We developed these parts to build the ultimate naturally aspirated BOSS while still giving great driving characteristics and engine response. We didn’t want a product that required changing other internal components in order to function or put the engine in danger of the valvetrain and cams getting out of control.” This strict adherence to Ford’s OE level engineering standards has yielded a product that is as bolt-in as any cam can possibly be.
Making It Thump
Installing this hardware sounds like a daunting task. It is true that a dual overhead cam engine is more complex than the old cam-in-block units. However, with the majority of the parts on top, this swap is no more difficult to perform. In fact after our experiences with modular engines over the last 18 years we’d rather swap the cams in an OHC engine than in the older OHV units any day.
Parts List
- M-9926-CJ65 65 mm Cobra Jet Billet Aluminum Throttle Body
- M-9424-M50CJ Cobra Jet 5.0 Intake Manifold
- M-9603-M50CJ Cobra Jet Cold Air Intake Kit
- M-6550-M50BEXH BOSS 302R Exhaust Cam (pair)
- M-6550-M50BINT BOSS 302 Intake Cam (pair)
With the new Ford Racing cams properly lubricated they were then installed and the rest of the installation was the reverse of removal. The biggest thing here is taking time to ensure all the timing marks are aligned properly during assembly. We capped things off with the Cobra Jet intake manifold, new big bore throttle body and Cobra Jet specific air intake.
Tuning
With Rhyne Cunningham tapping the keys, we put the modded BOSS on the rollers at Cunningham’s Motorsports to see what kind of power numbers the engine would make. The only other modification to our engine is a set of Bassani long tube headers, H-pipe, and cat-back exhaust. Ford Racing recommends long tubes with the use of these parts to take full advantage of the air being moved out by the new exhaust cams.
We baselined the car at 433.5 hp and 354.0 ft-lbs of torque to the rear tires on Cunningham’s Dyno. When Cunningham was done the BOSS had picked up 39.5 hp and 15.2 ft-lbs of torque at the rear tires for total power of 473.0 hp and 369.2 ft-lbs of torque. Those gains start coming on strong at 4,400 rpm and stay with the engine all the way to redline. Above 5,000 rpm the difference becomes even more dramatic as the cams take advantage of the improved airflow of the Cobra Jet intake and throttle body to make bigger power. Ford claims the Cobra Jet intake is tuned to peak at 7,750 rpm and that’s apparent from our dyno results, although we think the engine could have easily gone to 8,000 and probably continued to make power.
With everything in place we took the car out for a test drive. This BOSS is now badder than it ever was, and probably one step closer to how the Ford engineers behind the project envisioned the car would perform.