500HP On A Budget: 7.3L Power Stroke Edition
According to a bit of aged SEO data in this writer’s possession, the 7.3L Power Stroke was one of the most Googled diesel terms among its peers roughly six years ago. But is that still the case in 2021? Make a few phone calls to some companies that are in-the-know and you’ll find out that, sure, performance parts are still in high demand for the venerable 444 ci V-8. But why? Well, they don’t die—and nearly everyone knows that. And if you give them a chance to turn out some horsepower they can give you a solid ROI with nothing more than bolt-on, top-end parts in the mix. Like 500 to 550rwhp without sacrificing drivability or engine longevity…
Of course, you can make $1,100/month payments on a brand-new Super Duty if you want to. There’s always that option. But what if, instead of buying a $70,000 truck, you sunk $10,000 to $15,000 into your old workhorse for some extra giddy-up? With the parts list laid out below, we’ll show you what you need to do to run circles around the latest 1,000 lb-ft beasts leaving Detroit.
*Note: these recommendations are for ’94.5-’00 and select ’01-’02 engines, so long as they came from the factory with forged-steel connecting rods. Most 7.3L engines produced after ’00 were assembled with the weaker powdered-metal connecting rods, which are generally believed to be on the brink anywhere beyond 400rwhp and 800 lb-ft of torque.
T4 Turbo System
The path to 500rwhp on a 7.3L Power Stroke gets complicated quickly when you begin to compare the different turbo systems used between the ’94.5-’97, early ’99 and ’99.5-’03 engines. So we’ll cut right to the chase: buy an aftermarket T4 turbo system and never look back. A complete T4 turbo system, such as the kit offered by Irate Diesel, rids the ’94.5-’97 engine of its low-set, T4 divided collector and raises it so that a turbo with a bigger compressor housing can clear the driver side valve cover. On Super Duty versions of the 7.3L, a T4 system replaces the factory V-band turbine inlet arrangement. What this does is open the door to running the popular BorgWarner S300, S400 or T4 Garrett turbochargers on the market (the ones all the Cummins and Duramax guys are running). For 500 to 550rwhp, go with a T4 S366 SX-E or S369 SX-E.
Add An Intercooler (’94.5-‘97)
While it would make for a slight upgrade for ’99-’03 7.3L mills (which came from the factory with an air-to-air intercooler), the CSF intercooler is the ultimate budget-friendly intercooler for non-intercooled ’94.5-’97 engines. Installing it in the older Fords requires a bit of fabrication, but the results are 110-percent worth the effort. Exhaust gas temperature (EGT) will be more manageable and cooler, denser air will enter the heads. The increased efficiency can result in more horsepower and always provides a bump in torque. The CSF can be had for $250-$285 and its welded metal end tanks make it sufficient for handling big boost.
Aside from adding a chip, a considerable up-sizing of the fuel injectors is mandatory to get any kind of measurable horsepower out of a 7.3L Power Stroke. For us, the only option is to upgrade to a set of hybrid injectors, and specifically the 238cc version for 500hp goals. Around for roughly 15 years now, the 238cc hybrid is based off of an AB code injector (found in ’97 California 7.3L engines and all early ’99 versions), but is fitted with a larger diameter plunger and barrel from an I530E International engine’s injector while retaining the factory AB-code intensifier piston, hence making it a hybrid. The latter combination allows for a substantial increase in fuel flow without requiring more high-pressure oil to make it happen. This means a single high-pressure oil pump is all you’ll need to support it. The 238cc hybrid is combined with either an 80-percent or 100-percent over nozzle, which provides for a much quicker injection rate.
Electric Fuel System
The required supporting act for bigger injectors is an aftermarket fuel supply system with an electric lift pump. You can save money by piecing together your own or simply buy a comprehensive system with everything you need. On ’94.5-’97 engines, you’ll have to scrap the factory mechanical (cam-driven) lift pump in the valley. On ’99-’03 mills, larger fuel lines and a stronger electric lift pump (such as the common Walbro GSL392) is needed to support the hybrid injectors. On both engines, it’s best to delete the factory fuel filter housing from the valley as it opens up tremendous space under the hood, along with eliminating a potential leak point. Most all-inclusive aftermarket kits come with a regulated return system, complete with a fuel pressure regulator and a fuel pressure gauge to help you set your pressure exactly where you want it (65-68 psi, give or take).
Supporting the hybrid injectors on the oil side, a direct-replacement high-pressure oil pump called the Adrenaline (from DieselSite) is a household name. It’s a high volume HPOP that has proven more efficient than a factory pump, is capable of supporting up to a 285cc hybrid injectors and is just as reliable as the OEM unit. Among a host of internal improvements over stock, it features slightly more swash-plate angle (roughly 21 degrees vs. 17-degrees on a ’99.5-’03 HPOP). In conjunction with 238/80 hybrids, we’ve seen this pump support more than 500rwhp on the chassis dyno.
ARP Head Studs
With more fuel, a better HPOP and a high-flow turbo system aboard a 7.3L, the amount of boost pressure you see will easily exceed 40-psi (for reference, stock is 15-17 psi). This type of boost (and the drive pressure that comes with it) can eventually stretch the factory head bolts and lead to a blown head gasket. To rule this out, a set of ARP head studs has to be on your parts list. The good news is that you don’t have to pull the heads and start with fresh gaskets to install them. 7.3L gurus have long employed the practice of installing head studs one at a time and gotten away with it. ARP studs can keep a 7.3L’s factory head gaskets alive with as much as 75-psi of boost in the mix, which is pretty impressive. Beyond that boost level, it’s time for fire-rings or O-rings.
Stiffer Valve Springs, Stronger Pushrods
Another issue to address with 40-psi or more of boost in the mix is the factory valve springs. At elevated boost levels, the intake valves can creep open. And perhaps even worse, with excess drive pressure (which comes with higher boost levels), the exhaust valves can creep open during the intake stroke, polluting the intake charge. Comp Cams’ budget-friendly 910 valve springs have long been a go-to valvetrain upgrade for the 7.3L crowd. With the appropriate shims installed, the 910 valve springs can increase seat pressure to between 110 and 130 lbs (vs. 71-79 lbs stock). Valve springs can be installed once cylinder at a time, so long as each hole you’re working on is sitting at TDC before you begin and you have an overhead valve spring compressor tool at your disposal. Last but not least, a thicker wall set of chromoly pushrods such as the versions offered by Smith Brothers Pushrods is a must with any higher horsepower 7.3L build.
To tame the upgraded injection system, ensure the overall setup provides good drivability and (of course) ensure that you to clear 500rwhp, custom tuning of the 7.3L’s PCM is mandatory. The Hydra Chip platform from Power Hungry Performance has been the industry standard for years and allows the custom tuner of your choice to provide you with up to 15 different files, all of which are available on the fly via the digital display. If you spring for the optional USB extension cable with your Hydra, you’ll never have to pull the PCM again to retune your truck. For $25 extra, it’s more than worth it. As for finding a custom tuner, conduct your own research. Join an online forum or call a reputable shop for advice. Our best advice on the tuning front is to not tow at 500rwhp, leave that power level for play time. Have your tuner develop a tow tune (or several tow tunes) for your specific needs (weight, trailer type, etc.) and keep things in the 400rwhp range. Big torque (1,000 lb-ft via a 500rwhp tune) combined with a big load in tow is dangerous for any stock-bottom end 7.3L, forged rods or not.
More From Driving Line
- Need a good reason to justify dropping $10K to $15K into your ancient 7.3L Power Stroke? As one of the engines to make our “Unkillable Diesels” list, even with added power they are hard to kill.