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Keeping Pace, Part 1: 500hp 7.3L Recipe

Make Your 7.3L A Contender Without Sacrificing Durability

A quarter century ago, Ford’s HEUI-injected 7.3L Power Stroke was state-of-the-art. These days however, your ’94.5-’03 Ford is way behind the times. But just because brand-new diesels are packing 400 hp or more and 1,000-plus lb-ft of torque from the factory doesn’t mean your old workhorse can’t be made to compete. On the contrary, a thriving aftermarket continues to provide full support for Ford’s first Power Stroke—and breaking the 500hp barrier isn’t as difficult as you think. Even better yet, you can have your cake and eat it, too. As in, you can enjoy your newfound power without sacrificing reliability, provided you piece together the right combination of parts.

This month, we’re showing you the most effective path to 500-rwhp, and beyond. It’s a blueprint we’ve seen play out countless times on the chassis dyno, at the drag strip, and out in the real world. From picking the right injector to satisfying your high-pressure oil and low-pressure fuel supply needs, to installing a completely different turbo system and choosing the perfect charger, to making necessary valvetrain upgrades to sustain the added boost, drive pressure and rpm, we’re covering all the bases here. By no means is a 500hp 7.3L cheap to achieve, but it sure beats making a truck payment on a late-model diesel saddled with the latest emissions equipment. Go ahead, invest in old reliable. You’ll be glad you did!

Connecting Rod Disclaimer

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Because literally all of the mods in our 500hp recipe essentially revolve around stacking horsepower on top of a factory bottom end, it pays to identify which factory connecting rods resides in your 7.3L Power Stroke before diving in. If you’re working with a ’94.5-’97 engine or a ’99-’00 Super Duty engine, you’ve got forged rods and you’re fine. However, if you have an ’01-’02 model year 7.3L you need to find out whether or not you have powdered metal connecting rods or the stronger forged-steel units. With powdered metal rods (left), you’re advised to draw the line at 400 to 450-rwhp. For forged-steel rods (right), you’re good for 600-rwhp (and sometimes even more than that). Below are the production runs of forged vs. powdered metal connecting rods according to engine serial numbers:

  • Forged Steel Rods: Beginning of production – serial number 1425746
  • Powdered Metal Rods: Serial number 1425747 – 1440712
  • Forged Steel Rods: Serial number 1440713 – 1498318
  • Powdered Metal Rods: Serial number 1498319 – final production
First things first, an injector upgrade is mandatory for any 7.3L owner looking to make substantial horsepower gains. The AA-code single shot injectors in ’94.5-’97 engines flow just 95-98cc’s of fuel, early ’99 AB-codes flow 120cc’s, and ’99.5-’03 AD-codes flow 140cc’s. For their ability to increase fuel flow without requiring more high-pressure oil, what’s known as a hybrid injector is the best option. Specifically, a 238/80 (238cc’s worth of flow, 80-percent larger nozzle) hybrid, or “standard hybrid,” or a 250/100 hybrid is ideal for the 500 to 550-rwhp realm. These are offered by Full Force Diesel and Unlimited Diesel Performance, respectively. Why are they the perfect size injectors for this power range? Because a factory, 17-degree (‘99.5-’03) high-pressure oil pump can support their oil needs. However, the 15-degree HPOP found on ’94.5-early ’99 engines will likely need to be upgraded, but installing a 17-degree HPOP is an affordable, easy change to make.
So what’s the secret behind a hybrid requiring no additional high-pressure oil to achieve its performance gains? It starts with the use of a BD-code plunger and barrel out of an injector from Navistar’s I530E engine. The I530E-derived plunger and barrel fits within the 7.3L injector’s body without the need to machine anything, and its use effectively increases the bore of the injector. But because the hybrid retains the stock 16mm intensifier piston, it requires less oil to actuate it than a BD-code injector. Single shot injectors, rather than the split-shot units that debuted in ’97 California models and came factory in all ‘99’03 7.3L’s, are preferred when you get into aftermarket injectors for the 7.3L. This requires custom PCM tuning to get them to function properly (more on that later).
The other key piece in the injector puzzle lies in the nozzle. Larger diameter orifices in the injector tip allow more fuel to be injected per combustion event, and in a quicker window of time. This quicker injection rate means more efficient horsepower and less heat (i.e. stress) for the engine to have to deal with. Most aftermarket 7.3L injector nozzles retain the factory 7-hole design. An 80-percent larger nozzle is shown here, and each of its orifices measure 0.0075-inches (vs. 0.0060-inches stock).
Regulated return fuel systems are vital in protecting your injector investment. They are one of those mods that goes unseen or even mentioned, but plays a huge role in the overall performance of the injection system. By tying both fuel rails together via a bypass style adjustable pressure regulator, consistent fuel supply is delivered to each injector. The general consensus on fuel pressure delivered to 7.3L injectors is 65 psi.
To properly support a set of hybrid injectors, neither the mechanical or electric lift pumps that came stock on the ’94.5-’97 or ’99-’03 7.3L’s will work. On ’94.5-’97 engines, upgrading to an electric lift pump often entails a complete reworking of the fuel supply system, but a serious overhaul is also required on later engines (the aforementioned ’99-’03 models) in order to reach 500-rwhp. Popular lift pumps that can easily get the job done are the proven Walbro GSL392, Fuelab’s Prodigy, and the Aeromotive A1000. Each will support considerable horsepower, though the Prodigy and A1000 will support north of 600-rwhp, no problem. Complete, tank-to-engine fuel supply systems capable of supporting 500-rwhp or more can be had from Bean Machine, DieselSite, Driven Diesel (shown), and Irate Diesel.
Appropriately sized fuel hose must be paired with the right lift pump, and most aftermarket systems come with ½-inch line from the tank toward the engine, but we’ve also seen 3/8-inch hose support 500-rwhp on the dyno. By comparison, the factory fuel lines on an OBS Ford measure just 5/16-inches in diameter. Before reaching the engine, most fuel systems reduce fuel supply down to two 3/8-inch sections before joining the fittings in the rear of each cylinder head.
Deciding what to do at the origin of fuel supply, the tank, is also important. On OBS trucks with dual tanks, many opt to keep the factory selector valve. And although its 5/16-inch internal passages are restrictive, the selector valve can support 500-rwhp. We’ve even seen 540-rwhp squeaked out of it in the past. However, those looking to run a sump will have to either eliminate the use of one tank, or concoct a way to transfer fuel into the tank with the sump. For Super Duty owners, the choices are a little clearer: run a larger diameter draw straw in the tank or run a sump. Hint for OBS owners, if you delete the factory selector valve from your fuel system make sure it remains plugged in along the frame rail. Otherwise your fuel gauge won’t work…
To reiterate, part of the appeal of hybrid injectors is their ability to make solid power without requiring additional high-pressure oil volume. A healthy 17-degree OEM high-pressure oil pump (’99.5-’03 engines) will support a 500hp effort from a 238cc to 250cc injector. As for the 15-degree HPOP (’94.5-’97 and early ‘99), small-to-moderate hybrid injectors are beyond what it can support, so many either switch to a later, 17-degree Super Duty pump or install an aftermarket HPOP like the one shown here, the Adrenaline from DieselSite, which boasts a longer stroke swash plate (roughly a 21-degree pump).
For years, 7.3L Power Stroke owners were limited by having to run drop-in turbo upgrades. Granted, many of them could support 400 to 450-rwhp and some could even handle 500-rwhp (Garrett GTP38R), but options to upgrade or try different turbos were few and far between. This is where complete turbo systems like the one manufactured by Irate Diesel Performance revolutionized the 7.3L aftermarket. By introducing a high-mounted T4 exhaust collector with the corresponding pedestal, up-pipes, and intercooler piping, Irate’s systems allow a 7.3L owner to run virtually any BorgWarner S300, S400, or T4 foot Garrett charger. This was huge, as it opened up airflow tremendously, but it also allowed Ford owners to use the same proven turbochargers that Duramax and Cummins had been running for years.
All-inclusive, Irate Diesel’s T4 turbo mounting kits come with practically everything you need to transform the forced induction side of your 7.3L. A two-piece downpipe (4-inch for Super Duty’s, 3-inch on OBS trucks due to firewall clearance), 3-inch intake Y, 304 stainless steel intercooler pipes, a T4 exhaust collector and 304 stainless up-pipe assembly, turbo pedestal, all necessary external oil feed and return lines, and a cold air intake tube is included. Of course, other options can be added, such as the specific turbo you want to run, intercooler boots and clamps, ceramic coating, and steel 3-inch intake plenums.
Since T4 turbo mounting kits debuted for the 7.3L Power Stroke, turbo technology has improved. One hot-ticket turbo that matches well with 238/80 hybrids is BorgWarner’s 66mm S366 SX-E. The SX-E version of the S366 outflows its predecessor, the S366 SX3, 87 lbs/minute to 78 lbs/minute (or roughly 1,240 cfm vs. 1,115 cfm). With the latter charger (the S366 SX3) capable of supporting 500-rwhp when combined with a set of 238/80 hybrids, it’s no wonder why the SX-E version supports a solid 525-rwhp. On top of that, the forged milled wheel (FMW) S366 SX-E is quick-spooling and well-suited for towing. The trick is to order it with the looser, 1.00 A/R exhaust housing to help limit drive pressure.
Pushing things into 550-rwhp territory is the combination of a 238cc or 250cc hybrid injector and an S369 SX-E or S372 SX-E. Both of these S300 frame BorgWarner turbos utilize the same 73/80mm turbine wheel but outflow the 66mm SX-E thanks to their larger FMW compressors. Like the S366 SX-E, you get quick spool up and sound drivability with either of these chargers, but the tighter exhaust housing option (.91 A/R) is advised when combining them with 238cc to 250cc hybrids.
One of the most vetted turbochargers in the 7.3L aftermarket is the BorgWarner S467.7. This large frame turbo can support as much as 650-rwhp in applications running big hybrid injectors, but is also at home in milder, 500 to 550-rwhp setups. When paired with a set of mid-range hybrids such as 238cc or 250cc injectors, going with the 1.00 or even .90 A/R exhaust housing option will help keep spool up reasonable and moderately heavy towing on the table.
Freeing up airflow between the compressor side of the turbo and the engine is a big deal on the 7.3L, and it’s also why a T4 turbo mounting system requires that early Power Strokes be fitted with 3-inch intake plenums. On ’94.5-’97 and early ’99 7.3L’s the opening measures just 2-inches (3-inch units came on all ’99.5-’03 engines), and the restrictive units flow just 240 cfm. By opening them up to 3-inches, flow increases to nearly 540 cfm. The result is quicker response, cooler EGT, and more horsepower. And while Super Duty 3-inch plenums can be installed on early 7.3L engines, in OBS trucks we’ve found clearance issues when running them in conjunction with an S400. The solution here was Irate Diesel’s lower profile intake plenums (shown).
When it comes to EGT management, the factory intercooler that came on all ’99-’03 Super Duty’s will suffice, so long as good PCM tuning is also in play to help keep piston-melting temps from building. For the non-intercooled OBS trucks, an intercooler isn’t a suggestion, it’s mandatory—especially if you want to tow. Installing an intercooler in a ’94.5-’97 Ford is a lengthy, highly-involved process, but the benefit is engine-saving EGT control and cooler, denser intake temps all around.
Sourcing an aluminum 7.3L Super Duty intercooler or repurposing one out of a 6.0L Power Stroke application is common for OBS owners looking to intercool. However, the aluminum replacement intercooler from CSF is perhaps the highest value you’ll find in the 7.3L aftermarket. It features welded metal end tanks, holds more than 50-psi of boost without issue, and can be purchased (brand-new) for $285. It doesn’t get any more “budget friendly” than that.
Quick spooling turbos capable of forcing 45 to 50 psi of boost into an engine sounds great—until your truck defuels. On all Super Duty’s and even select OBS trucks, a boost fooler is mandatory. Around 23-24 psi of boost, the Service Engine Soon light will illuminate on ’99-’03 Fords, and the PCM will pull fuel in order to lower boost pressure. When defueling issues arise in OBS trucks, it’s usually because the MAP sensor sees boost building too quickly. In either case, a boost fooler like Driven Diesel’s Overboost Annihilator solves everything. The high-quality, adjustable pressure regulator tricks the PCM and MAP sensor into only seeing a maximum of 22-23 psi.
Last but not least (and actually, most importantly) for the injection system is tuning—and specifically custom tuning. To glean the most performance out of a set of hybrid injectors and a T4 turbo system, your custom-tailored PCM tuning should be handled by a reputable, competent dealer or calibrator, and also someone who’s worked with your exact turbo and injector combination in the past. On top of that, they should know exactly how to keep timing in check (especially at low rpm) and how much injector duration (i.e. pulse width, or injection on-time) to command to achieve 500 to 550-rwhp and not melt down your engine.
Then, because moderately-sized hybrids and an S300 or smaller S400 can still be used to tow with, comes the fine art of de-tuning a 7.3L to be able to still be reliably worked. Later transmission shift points, firmer shifts, a later third gear lockup event and Overdrive shift, and keeping EGT from ever cresting 1,250 degrees sustained can all be accomplished by toning down the hybrids with a 325 to 400-rwhp tow tune. That brings us to another important point: don’t tow on your max effort, 500 to 550-rwhp tune. Well, at least if you want your stock bottom end to live.
The most popular tuning platform in the 7.3L world is the Hydra Chip from Power Hungry Performance, which are programmed using tunes created via PHP’s Minotaur software. With 15 customizable positions available on the fly plus a Module Bypass and No Start position built right into it, the Hydra is the tuning method of choice in nearly every high-horsepower 7.3L we come across. Another popular means of tuning a 7.3L is the time-tested (and highly-affordable) six-position chip produced by TS Performance.
One of the biggest weak links in the 7.3L Power Stroke exists in its valve springs. The flimsy factory springs have a rated seat pressure that ranges between 71 and 79 lbs, so who knows what is actually the case in a 200,000-mile engine. At a minimum, the tried and true Comp Cams 910-16 valve springs, which can be shimmed to provide roughly a 110 to 115-lb seat pressure (good for a 500hp application), should replace the stockers. For higher power levels or a bit of overkill, competition valve springs such as the units available through Irate Diesel carry a 150-lb seat pressure.
With higher rpm, more boost, and even more drive pressure, the 7.3L’s bend-friendly factory pushrods are known to become a weak link. Thanks to companies like Smith Brothers Pushrods and Hamilton Cams, superior aftermarket drop-in replacements rule out this failure point for good. Here, you’re looking at Hamilton’s stock-length, 4130 chromoly pushrods. A 0.095-inch wall thickness, 3/8-inch o.d. and hardened, pressed-in 8620 ball ends make them significantly stronger than the OEM units.
Thanks to leaving the assembly line with six head bolts per cylinder, the 7.3L can handle 40-psi of boost and sometimes even more before blown head gaskets become a worry. However, on higher mile engines the risk of popping a head gasket only increases, so we consider ARP head studs a must-have insurance item in any 500hp 7.3L build. You can either do it now, or do it later—along with dealing with a mess if you choose to wait. With head studs in the mix, your 7.3L is good for handling 75-psi of boost, which a 500-550-rwhp 7.3L with a properly sized turbo will never see (think more along the lines of 45-55 psi).
It isn’t the “right” way to do it, but we’ve seen the one-at-a-time install trick for head studs work on many engines over the years. This method forgoes pulling the heads by removing a head bolt and replacing it with a head stud one at a time. Some 7.3L die-hards swear by the process, adding that if you don’t over-torque the head studs you can always reuse them if you do end up losing a head gasket later on down the road.
On the opposite side of the fence of the head stud install debate, you’ll find 7.3L owners that want to make sure their heads and their block’s deck surfaces are as true as possible. By pulling the heads, having everything checked out, and visiting the machine shop if need-be, it’s great peace of mind for anyone looking to make 500-rwhp or more reliably.
Chassis dynos can vary, trust us. But we can tell you that the following recipes earned their numbers on two of the most accurate dynos in existence. For the 502-rwhp and 906 lb-ft graph that’s depicted here, your local results may be slightly higher, but likely won’t be lower. The parts list entailed an Irate Diesel T4 turbo mounting system, BorgWarner S366 SX3, Spearco intercooler, 3-inch intake plenums, Unlimited Diesel Performance 238/80 hybrids, a DieselSite Adrenaline HPOP and CPR fuel supply system with a Walbro GSL392 lift pump, and a regulated return. Hard-part mods boiled down to ARP head studs, Comp Cams 910 valve springs, and Hamilton chromoly pushrods.
In a textbook example of how a good tuner whose goal is to keep the rotating assembly from grenading (in this case, Matt Robinson of Gearhead Sales), a 200,000-mile stock bottom-end 7.3L equipped with an S467.7, 250cc hybrids, and all the other supporting mods laid down 555hp and 917 lb-ft of torque. By waiting until 2,800 rpm to ramp up timing, the factory forged steel rods aren’t forced to deal with 1,100 to 1,200 lb-ft of torque—the type of torque that bends rods. In fact, the entire performance tune is safe, with just 14 degrees of overall timing advancement commanded at 3,200 rpm. This same stock bottom-end 7.3L is still running today, nine years after this dyno graph was achieved.
It would be reckless not to mention the hell your E4OD or 4R100 is going to catch (should you own a ’94.5-‘03 truck with an automatic) with running hybrids, a race-ready fuel system, and a high-flow turbo. A triple-disc torque converter with a billet front cover, a resurfaced pump, upgraded clutches, 300M billet steel input and intermediate shafts, and a cryogenically treated output shaft are common upgrades for these old-school four-speeds. A properly-built valve body that provides firm shifts yet not dash-rattling bangs is a key part of any well-built E4OD or 4R100, too. Of course, special care should also be taken to fix the inherent problems present in the E4OD and 4R100 transmissions’ designs, a few of which are reverse hub reinforcement, a larger retaining snap ring in the coast clutch drum, and the forward drum plug being replaced with a permanent set screw.

SOURCES

Aeromotive

913.647.7300

aeromotiveinc.com

ARP

800.826.3045

arp-bolts.com

Bean Machine

844.237.7467

bdpshop.com

DieselSite

888.414.3457

dieselsite.com

Driven Diesel

Drivendiesel.com

Fuelab

618.344.3300

fuelab.com

Full Force Diesel

615.962.8291

shop.fullforcediesel.com

Irate Diesel Performance

503.435.9599

iratediesel.com

Hamilton Cams

512.355.9101

hamiltoncams.com

Power Hungry Performance

678.890.1110

powerhungryperformance.com

Riffraff Diesel Performance

541.879.1052

riffraffdiesel.com

Strictly Diesel

623.582.4404

strictlydiesel.com

Summit Racing (Comp Cams)

800.230.3030

summitracing.com

TS Performance
270.746.9999

tsperformance.com

Unlimited Diesel Performance

740.569.1319

unlimiteddiesel.com

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