Paw Paw Gone: 600-HP F-250

This Ain’t Your Grandpa’s OBS Ford

Occasionally, we come across a truck that puzzles us. No matter how much abuse it sees, for some unknown reason, it never breaks anything—even though we know damn well it should. This scenario plays out day after day for Robby Ching and his 7.3L-powered ’97 F-250. The 600-hp old body style Ford knocks down low 12s and makes boosted four-wheel drive launches on a regular basis, yet still sports a 300,000-mile stock bottom end and the front Dana 50 TTB.

“People always say to me: ‘I don’t know how your truck is still holding together,’” he told us.

While the Dana 50 TTB has been reliable so far (probably due to its stock ride height), Robby did tell us the truck will get a solid axle swap if it ever gives him any problems. His rationale for keeping the twin traction beam under the truck is that it’s yet to fail or give him any reason to replace it.

But it gets better. The truck serves three purposes for Robby: work truck, daily driver, and play toy. After being hooked to a trailer Monday through Friday, it hits the quarter-mile or dirt drags on the weekends, along with being his primary means of transportation. While a lot of big power, stock bottom end 7.3L owners worry about when they’ll scatter parts, Robby is out racking up 3,500 miles a month in his.

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Smart Start

Purchased with nothing more than a TS Performance chip and 180,000 miles on the odometer, Robby started modifying the truck immediately. Keeping things simple on the engine, he only upgraded the weak links that the 7.3L Power Stroke valvetrain is known for, along with adding head studs. A set of Comp Cams 910 valve springs replaced the factory springs, and the stock pushrods were ditched in favor of Smith Brothers chromoly units.

“I can drag race it and have a ball on the weekend, and then I’m hooked to the trailer and back to work with it on Monday.” —Robby Ching

To keep the heads from lifting, a set of ARP head studs was threaded in one fastener at a time (a trick used to save the existing head gaskets). To date, the heads have never been off of the block.

Bigger is Better

After sporting a set of 238/100 hybrid injectors for a while, Robby decided to upgrade to a set of Full Force Diesel 300/200’s about 10,000 miles ago. He hasn’t looked back since. The big hybrids receive a steady diet of diesel thanks to a Marty’s Diesel Performance electric lift pump system, complete with a regulated return and Aeromotive regulator. A Stealth SRP1.1 high-pressure oil pump keeps up with the oil demands of the injectors, and completes the HEUI injection system. On the tuning side, Robby navigates through his Swamp’s Diesel Performance tunes courtesy of a TS Performance six-position chip.

For boosted, four-wheel drive launches, Robby uses 3-inch, 10,000-lb. ratchet straps to clamp the frame and leaf springs down. This keeps the front end from chattering and is likely what has kept the twin traction beam in one piece. The ratchet straps also keep the front end digging, as Robby told us the truck runs three tenths of a second slower at the dirt drags without them.

Marty’s Diesel Performance supplied the electric lift pump system, which incorporates the proven Walbro GSL392 pump, CAT water separator and fuel filter and a regulated return system. Running this fuel system, Robby was able to squeeze just under 600 hp worth of power through the factory selector valve! As we went to press, Robby was in the midst of scrapping both factory fuel tanks, installing a Bronco tank in the rear and adding another Walbro pump to the equation in order to maintain ample fuel pressure to the injectors.

With the heads still on the block, Robby installed Comp Cams 910 valve springs, swapped in a set of Smith Brothers 4130 chromoly pushrods and installed ARP head studs one at a time. A set of Full Force Diesel Stage 3 300/200 hybrid injectors and an SRP1.1 high-pressure oil pump effectively place the HEUI injection system on steroids.

T4 Turbo

Thanks to a T4 turbo mount built by Stroker’s Unlimited, the popular S467.7 charger from BorgWarner sits at the back of the lifter valley. Stroker’s Unlimited also fabricated a set of stainless steel up-pipes and all intercooler plumbing. An aluminum intercooler from a 7.3L Super Duty application is employed to keep EGT cool while towing. Under wide open throttle and in Overdrive, the engine sees more than 60 psi worth of boost.

“More than 60 psi worth of boost.”

Tranny Work

Transferring power to the ground is an E4OD automatic that was put together by The Gear Box, a local transmission specialist in Robby’s neck of the woods. A triple disc torque converter from FTI Performance gets things started, while the rest of the four-speed is graced with upgraded clutches, a custom tuned valve body, and billet input and intermediate shafts. It sees full-time towing duty, plenty of boosted launches, and its fair share of vigorous street driving on a regular basis.

Keeping the transmission build local, Robby had The Gear Box of Mechanicsville, Maryland, fortify the E4OD automatic. The old-school four-speed would receive a host of upgraded internals, including billet input and intermediate shafts, clutches, and a custom-tailored valve body. A triple disc torque converter from FTI Performance tops off the transmission’s list of modifications.

Just as Robby stated, his OBS is a work truck first and foremost. Monday through Friday it’s typical to find a 10,000-lb. construction trailer attached to it, but occasionally it sees much larger payloads. This one tipped the scales at 31,280 lbs. (truck and trailer combined).

Conveniently mounted on the dash is the key to navigating a whole host of nasty tunes. Robby chose to have the guys at Swamp’s Diesel Performance handle his custom PCM tuning needs by way of burning them onto a TS Performance six-position chip.

While a lot of stock (forged rod) bottom end 7.3L Power Strokes live at elevated horsepower levels a while, Robby’s has been living life at the 500-plus mark for nearly 120,000 miles. It seems to contradict nearly everything we hear about highly modified 7.3Ls. And the fact that he’s never broken or had to rebuild anything in the Dana 50 front end defies all logic, given what he’s put the truck through. To date, it’s been a reliable daily driven workhorse, a consistent 12-second performer at the track, and a complete sleeper on the street. Yes sir, this is definitely not your grandpa’s OBS Ford.

Believe it or not, Robby was in search of a Super Duty when he came across the truck. But going with an OBS has definitely paid off in the go-fast department. The truck’s lightweight, and fuel and air modifications easily turned it into a low 12-second performer at the dragstrip.

Although Robby has had his share of traction issues during four-wheel drive launches at the dragstrip, it’s a whole other story when he launches in the dirt. Watching this thing in person, it digs and leaves harder than most solid axle trucks making power—a testament to the maximum traction nature of the infamous TTB Dana 50.

[divider]Specs[/divider]

Year/Make/Model: 1997 Ford F-250
Owner: Robby Ching
Hometown: Leonardtown, Maryland
Odometer: 294,287 miles
Engine: 7.3L Power Stroke with ARP head studs, Comp Cams 910 valve springs, Smith Brothers chromoly pushrods
Fuel: Full Force Diesel 300/200 hybrid injectors, Marty’s Diesel Performance 875 Kit (electric fuel system) with Walbro GSL392 pump and regulated return
Oil: Stealth SRP1.1 high-pressure oil pump
Air: BorgWarner S467.7 FMW turbo with race cover, Stroker’s Unlimited custom T4 mount with stainless up-pipes and intercooler piping, 7.3L Super Duty aluminum intercooler
Tuning: Swamp’s Diesel Performance via TS Performance six-position chip
Transmission: The Gear Box E4OD transmission with billet input and intermediate shafts, custom valve body, FTI Performance triple disc torque converter
Horsepower: 595 hp (dyno/track confirmed)
Torque: 1,138 lb-ft. (dyno confirmed)
Tires: 285/75R16 Bridgestone Dueler A/T
Wheels: 16×7-inch factory Alcoas
Axles: 3.55 gears, Warn front manual locking hubs
Suspension: Homemade traction bars, 3-inch 10,000-lb. ratchet straps for front end

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Pinaki Bhattacharya

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