How 7.3L’s Are Making Quick And Consistent 7.70, 6.70, and 5.90 Index Passes

Everyone loves an underdog. And in the world of diesel drag racing it doesn’t get much more “long-shot” status than it does with the 7.3L Power Stroke. Still, there are a select few that continue to choose to campaign these early electronically-controlled relics in modern times. It’s a race program that’s built on some of the most cutting-edge 7.3L parts you’ll find anywhere, but believe it or not the horsepower recipes are simpler than one might initially think. Big hybrid injectors, increased high-pressure oil volume, ample low-pressure fuel supply, and sound PCM tuning all allow the factory HEUI injection system to be retained while making north of 1,000 hp. And taking cues from the Cummins crowd, big single turbochargers and nitrous are the norm as well.

This month, we’re showcasing several examples of 7.3L owners who race in the Outlaw Diesel Super Series’ 7.70 Index, 6.70 Index, and even its 5.90 Index classes. In the eighth-mile, two of them have even dipped deep into the 5’s, including a 5.46-second blast and a 5.72-second effort. The 7.70 Index candidate has been as quick as 7.0 in the ‘660, 11.0 in the quarter, still gets daily-driven, tows, hauls, and regularly partakes in cross-country camping trips. To watch these trucks continue to defy the odds in diesel drag racing, look for them at an ODSS event near you this summer.

As horsepower increases and drag racing goals become more serious, the 7.3L Power Stroke inevitably requires a built bottom end. Upgraded rods, thermal and dry-film coated pistons, crankcase girdles or bed plates, ARP main studs, half-filled water jackets, and fire-ring grooves are all employed to ready a 7.3L for elevated boost and cylinder pressure.
While built engines are typical (as well as advised) for index racing 7.3L’s, it isn’t completely necessary. Take Matt Maier’s 7.70 Index OBS Ford for example. He competed on a stock forged-rod bottom end for years before the engine dropped compression (due to bent rods), forcing him to break the seal and make some upgrades.
While there are many weak links within the 7.3L’s factory long block, the primary reason for reinforcing one for coping with higher horsepower is due to the stock connecting rods’ propensity to fail. High-quality, proven aftermarket replacements include the forged Ultimax rods from Hypermax, Carrillo’s H-beam units, the ProHD series from Brian Crower, and the Pro I-beam rods offered by Manley (shown here).
OEM-derived, cast-aluminum pistons are par for the course in most built 7.3L engines in index racing, albeit with a few key tweaks. De-lipping (removing the sharp edge from the factory fuel bowl), valve relieving (typically for high-rpm valve clearance), and special coatings are all common here, the latter usually consisting of a ceramic, thermal barrier up top to hold up to extreme EGT and a dry-film lubricant for reduced friction on the skirts. We’ll note that low-friction, DLC coatings are used on 7.3L wrist pins in many circumstances, too.
In the same arena as a factory 12-valve Cummins head, the 7.3L’s cast-iron heads flow terribly in stock form. This produces a fuel-only horsepower wall of roughly 650-rwhp on most trucks. Shops like Carson Stauffer, Swamps, and Crutchfield Machine have seen tremendous results from porting 7.3L heads, the latter company having sponsored a set that unlocked an additional 100hp in Brian Jelich’s ’00 Super Duty—a 1,000hp truck that was both streetable and running 6’s in the eighth-mile at the time.
Although it took years to get manufacturers to bring an aftermarket camshaft for the 7.3L to market, the results—especially when combined with the aforementioned ported heads—have been impressive. With a cam like what’s offered by Colt Cams or Gearhead Sales you have the ability to both introduce fresh air quicker and rid the cylinders of heat faster, which means quicker spool up, added high-rpm power, and reduced EGT. A cam upgrade isn’t a prerequisite for a high-horsepower 7.3L, but it certainly makes one more drivable on the street and user-friendly at the track.
For their ability to hold down the fort, even in non-fire-ring applications that see 75-psi of boost, ARP head studs are up to the task. In fire-ringed engines, upward of 75-psi (along with triple-digit drive pressure) remains a non-issue for these time-tested fasteners.
In nearly every high-horsepower 7.3L build these days, you’ll find a dual high-pressure oil pump combination lurking at the front of the lifter valley. Whether it’s a dual HPOP kit from Full Force Diesel or a Swamps Gen3 residing over a stock HPOP, either combination can support the high-pressure oil needs of virtually any 7.3L injector ever offered. Supported by a higher volume low-pressure oil pump such as a Melling LPOP or especially DieselSite’s LPOP, there is no stopping a dual HPOP 7.3L from feeding all the oil in the world to a set of massive injectors.
A key piece in the power-making puzzle is a sufficient low-pressure fuel supply system. A minimum of 65-psi needs to be delivered to the 7.3L’s injectors at all times, along with ample volume. Most aftermarket or homemade competition fuel systems entail at least ½-inch diameter feed lines, larger supply fittings in the heads (typically -6 AN), and a reputable lift pump along the frame rail. Fuelab or Aeromotive pumps usually get the nod in competition applications.
Competition level injectors used in the 7.3L realm range from 350cc hybrids equipped with 200-percent larger nozzles to 400cc, 400-percent over nozzle hybrids, to 455cc hybrids with 400-percent larger nozzles. In each instance, and with the right amount of low-pressure fuel supply (lift pump) and injection control pressure (ICP, or high-pressure oil) on tap, either size injector can support well north of 1,000 hp with the right amount of air (i.e. turbo and nitrous).
To keep fuel flow consistent to each cylinder, regulated return systems have not only become standard on competition 7.3L engines, but on modified 7.3L’s in general. Both fuel rails are tied in together via a bypass adjustable fuel pressure regulator, where the aforementioned (and optimum) 65-psi or higher pressure is set.
Be it due to avoided complexity, 444 cubic inches generally not having a problem with spooling a big single, or the fact that a single charger is easier on an engine, compound turbos aren’t common in the big power realm of the 7.3L segment. After all, a moderately-sized S400 frame turbo can be brought to life fairly quick during staging (such as in Matt Maier’s 7.70 Index case with an S467.7), and a small spool jet can help spin up a larger S400 if needed (such as in Brian Jelich’s 5.90 Index case with an S480). Here, the T4 turbo mounting system from Irate Diesel Performance aboard Matt Maier’s OBS is on display. For comparison sake, Brian Jelich’s higher-flowing T6 system was custom-fabricated by Paul’s Custom Fabrication and Machine for his one-off, front-mount-type turbo application.
While we could see more GT55 Garrett stuff creep into the 7.3L index racing world at some point, for now the BorgWarner S400 seems to be the snail of choice. But that doesn’t mean that all S400’s are created equal. In Matt Maier’s aforementioned 7.70 setup, a box T4 S467.7 FMW does the trick. However, in Brian Jelich’s 5.90 application—where elapsed times occasionally push into Pro Street territory—a T6 flange S480 from KC Turbos is employed. Jelich’s S480 is shown here, with the 80/96/1.32 A/R charger’s billet 13-blade compressor wheel exposed.
To be sure, all 7.3L’s are fuel-limited thanks to the HEUI system. This is why nitrous plays a role in making them competitive. And even though Matt Maier’s OBS Ford can run 7.70 Index on fuel, his 7.0 (eighth-mile) and 11.0 (quarter-mile) passes were only possible on spray (and equates to about 900-rwhp on spray, vs. 650-rwhp on fuel). As for Zack Pierce’s 6.70 and potentially soon-to-be 5.90 Index crew cab Super Duty, a fair amount of N20 is on tap to get his behemoth turning in the ET’s and trap speeds it does. As for Brian Jelich’s 5.90 setup, a surprisingly mild, two-stage setup is all he campaigns.
A whole other rabbit hole within the top ranks of 7.3L racers is tuning, and how tuners go about getting the most out of the giant hybrid injectors they’re forced to tame. Some tune their own while others rely on time-tested, track-proven calibrators to write their race-winning files for them. Regardless who is hitting the keystrokes, by and large most PCM’s are tuned using Power Hungry Performance’s Minotaur software—and most of those run a PHP Hydra Chip. 5.90 racer Brian Jelich tunes his own truck (and does so under the Jelibuilt Performance nameplate) while 7.70 driver Matt Maier prefers Gearhead Sales handles his.
Two-stage nitrous arrangements gets most index racing 7.3L’s where they need to be, but Matt Maier’s setup, which has been pushed north of 1,000 hp several times on the chassis dyno, holds a third stage (and a .157 jet) in reserve. Believe it or not, to make consistent 5.90 passes Brian Jelich’s nitrous arrangement only entails the use of a 0.30 spool jet and a .070 jet to get the job done.
Obviously most 7.3L die-hards are dyed-in-the-wool Ford fans also, which helps explain why the E4OD or 4R100 transmission usually remains in the mix when they take things to the next level. Brian’s Truck Shop, John Wood Automotive, Wyse Auto Repair, and Twisted Diesel-built transmissions have all been tried behind high-horsepower 7.3L’s with great success. The former builder was responsible for this one, a Level 4 version mounted in Brian Jelich’s 5.90 Super Duty. It conceals an Aermet input shaft, an oversized 300M intermediate, and a 300M output, along with a billet-steel forward drum and overdrive planetary, and a spragless, 1,900-rpm stall Precision Industries converter. Shift points and converter lockup are commanded via a TCM-2800 from Powertrain Control Solutions.
To get around the intermittent shifting issues caused by the OBS Ford factory electronics (in short, they can freak out when the transmission requires an upshift five times sooner than stock), Matt Maier built his own shift box. By having full control over both his shift points and when he locks the torque converter, Matt’s consistency at the drag strip improved considerably.
Matt Maier’s racing days go way back with his ’97 F-250, a truck he’s owned for 15 years now. With a solid 7.70 Index program, Matt went rounds at nearly all the national events he attended, and even won the 11.90 Index class two years in a row at the former Diesel Thunder race in Mississippi. When leaned on, his OBS has been as quick as 7.0 in the eighth and 11.0 in the quarter—not bad for a daily driver that still tows a 40-foot gooseneck!
Zack Pierce has been a regular 6.70 Index competitor on the ODSS scene over the years and claimed Third in points in 2021. Now, after having shown what his ’02 F-250 was truly capable of at Diesel Truck Wars last fall, he appears to be setting his sights on running 5.90 Index. With a 5.72-second pass at 122 mph under his belt at that event, his crew cab Super Duty definitely has what it takes to go rounds in a quicker racing category.
Though Zack will have to slow things down to run 5.90, it’s always easier to pull fuel and back things off than it is to have to engage in an all-out effort each pass. But even detuned, the big red Ford will have to apply roughly 1,300 hp to the track in order to turn in consistent 5.9-second passes. Based on what we’ve seen in the past, somehow we think his equipment will be up to the challenge…
Back in 2018, this was the 6.70 Index recipe Zack Pierce was running, but all of it is different now. Instead of the big single being mounted in the traditional location at the back of the lifter valley, the turbo (a larger, Garrett GTX5020R) is front-mounted. A 100-psi, Peterson-sourced wet sump oil system is in play now, too, along with a set of big-valve, worked-over Crutchfield Machine heads.
At 5,900 pounds, Zack Pierce’s first-generation Super Duty is about as stripped down as it gets—just look at the interior. More than 1,400 to 1,600 pounds has likely been removed from the crew cab short bed’s original heft.
David Beach’s super cab long bed OBS is yet to officially enter the ranks of ODSS, but under a previous owner it went 6.68 at 107 mph. In all likelihood that means David will be gunning for 6.70 Index. At approximately 6,600 pounds, running the class will call for roughly 1,100 hp each pass, not a big deal with a bit of spray. Already having a 7.70-second (low 12-second) Super Duty in his stable, making the jump to a quicker racing category is well within David’s (and his truck’s) capabilities.
With a race weight of 4,300 pounds, the built 7.3L engine in Brian Jelich’s fiberglass ’00 Super Duty barely breaks a sweat when it makes passes in 5.90 Index. In fact, Brian’s quickest pass in the truck so far, a 5.46 at 127 mph, required somewhere in the neighborhood of 1,250 hp at the wheels—which is far from leaning on the engine. With a brand-new 7.3L fitted with the latest and greatest parts in the works, expect more spray to be used during the course of his next “hero” pass—and a trip noticeably deeper into the 5’s.

 

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