Chuck James
May 30, 2004

About 10 minutes after fuel-injected 5.0 Mustangs rocketed intopopularity in the late '80s, box intake manifolds appeared. These wereupper intake boxes that roughly resembled an elongated shoe box or loafof bread and were bolted to the existing lower intake. Some weredesigned for the stock oval-runner lower intake, while others mated tothe "staggered-round" GT-40 lower.

The idea behind these intakes was simple. By reducing the long upperintake runners to mere stubs and fitting a blimp-hangar-like plenumarea, screaming top-end power would result. True, their designersrealized, torque and midrange power would be greatly reduced, but withunheard-of top-end power, the "box uppers" would make up for theirmissing torque with gears and top-end horsepower. These intakes werenever designed for bolt-on-type cars that absolutely require runnerlength for reasonable torque in the real world. In fact, theirapplication was mainly intended for supercharged drag engines whereblower boost would make the day starting in the midrange.

Three inches of runner length is the key feature of Trick Flow's newBox-R Intake Manifold. It really shows here in this upside-down viewof the assembly, along with the 90mm throttle body opening. Total runnerlength with this upper and an R-Series lower intake manifold is 9 incheson a 302 and 10.3 inches on a 351.

You'll notice you don't see many of these early box intakes aroundtoday. We could be trite and say they didn't work, but that's only ahalf-truth. The thinking behind the box intakes was sound, but theexecution always left insufficient runner length for the street. Theresult was a near total loss of low-end torque, enough so that thetop-end power bonanza wasn't enough to make up the lack of low-endpower.

Horse Sense: Of course, we know about TrickFlow's cylinder heads and intake manifolds, but the company has alsoexpanded into several other product lines. These include intake spacers,valve covers, cams, diff girdles, 4.6 intake elbows, and even nitrouskits.

Keep in mind the early box intakes were designed for the stock or GT-40intakes. The straw-runnered stocker was a nonstarter in this category,and even the otherwise great GT-40 didn't have large enough or straightenough runners to be a top-end star. But that's what was available inthe early years.

Furthermore, enthusiasts insisted on bolting the boxes to bolt-on carsor mildly boosted street drivers with predictable results. The badmouthing from these ill-advised, dissatisfied street stormers didn'thelp. Yet another factor was the lack of cubic inches. Early on, the 5.0phenomenon was a 302ci party. The 347s were still in the future, andwhile a few souls had transplanted 351 Windsors into their Foxes, thewidespread use of 392s and 408s was also years away.

One place where the box intakes did well was on forced-induction cars atthe dragstrip. There the combination of steep final drive gears, a dutycycle comprised solely of high rpm, and--most importantly--a bigsupercharger positively cramming the intake full of air ensuredsparkling top-end performance and enough midrange to make a go of it.

As the photos show, a new box intake from the airflow experts at TrickFlow Specialties has reached market. Again, the idea is to promotehigh-rpm horsepower on big-inch 347 and Windsor-based strokers, but thistime more development has gone into the runner length, the plenum shape,and other details to make this a superior performer.

For Pricing and Part information click the picture above.

It's obvious some runner length--just 3 inches--was incorporated into thedesign. While this length is definitely short, it's enough to broadenthe intake's working range so it has some midrange, while at the sametime providing Niagra Falls flow at the top end.

Trick Flow also has a range of lower intakes on which to perch its newupper. Their popular Street and Track Heat 302 manifolds use the samelower intake with 2.00x1.20-inch runner dimen- sions at the outletflange, while the racy R-Series and 351 Windsor lowers boast notablylarger 2.380x1.380-inch runners. Trick Flow is offering the new box, orBox-R Intake Manifold as it is officially known, only for the bigR-Series/ Windsor lower. That's proper, as the street-based 302 stuff issimply too small to support the box upper. This also means the newintake will fit both 302-based and 351 Windsor-based engines.

(above & right) On the discharge end of the runners, the staggered rectangle spacing isapparent, along with the recessed mounting hardware between the lowercasting and the billet flange adapter. The upper intake mates witheither the R-Series 302 or 351 Trick Flow lower intakes.

You'll also note the new Trick Flow box upper resembles Ford's '96-'98Cobra intake manifold. Trick Flow is quick to point out that they had nointention of copying the Ford intake, but rather that's where the flowbench led them. This makes perfect sense, as both intakes share the sameperformance criterion--high-rpm flow--and you know Ford spent plenty ofresources developing the Cobra intake so it would work. There's noreason to think Trick Flow's flow bench would take the company in anyother direction. Or, as Charlie Schmidt of Trick Flow told us, any othershape had dead areas in the plenum's corners.

Trick Flow gave the new intake a beau-tiful shape and classy badging,and the button-headed hardware is easy on the eyes as well. The uppercastings are available in raw aluminum as shown here, or powdercoatedsilver or black.

Other hallmarks of good airflow management are seen in the new intake'sperfectly straight and equally spaced runners. The somewhat raised androunded entries into the runners in the bottom of the new upper are alsocharacteristic of high-flow air practice. The throttle body inlet iscentered on the runners and sized for a 90mm unit. No EGR is provided tothe throttle body flange, and obviously no CARB E.O. number is availableas the intake is a race-only design.

The throttle body has also ended up rearward of its stock location,fouling the stock fuel rail/regulator arrangement. Aftermarket fuelrails are the answer to this. At our deadline, Trick Flow was working ona fuel rail to suit, but any number of aftermarket fuel rails andadjustable fuel regulators should work.

Careful shaping of the plenum cover directs air into the runners andprovides the intake with what is sure to become the modern "rounded box"standard in high-flow intake shapes. We doubt hand-grinding will do anygood, but the easy-to-manufacture, two-piece plenum design does alloweasy die-grinder access.

There should be enough slack in the stock throttle cable to work,however, and the 90mm inlet means grinding that opening should hardly benecessary. With no EGR available at the throttle body, Trick Flow offersa blank EGR spacer to properly space the throttle body.

Charlie at Trick Flow figures on a "1,200-1,300hp" potential from thisintake on a turbo'd Windsor race engine. That ought to be enough foranyone running a store-bought, cast-aluminum intake.

As for a lower horsepower level for the new Box-R intake, Trick Flowsays its standard R-Series intake starts losing to the new box upper at450 hp, while big-inch Windsors in the 408-cube league are ready for thebox upper at 550 hp.