O'Bryant Diesel Service Making Big Power And Winning Races With Diamond Pistons.

March 22, 2018 / by Bradley Iger

When it comes to high performance diesel builds, O’Bryant Diesel Service in Bethlehem, Kentucky, has quickly become one of the go-to shops for making big power. We take a look inside there operation and at there race-winning shop truck. 

When it comes to high performance diesel builds, O’Bryant Diesel Service in Bethlehem, Kentucky, has quickly become one of the go-to shops for making big power. “I became involved with truck and tractor pulling as an engine builder around 2007,” says Patrick O’Bryant. “At that point we were mainly just working on our personal puller and some friends’ trucks.”

Over the years O’Bryant’s workload continued to grow, eventually spurring him to establish O’Bryant Diesel Service in 2013. “Our main focus is engine building for the truck and tractor pulling market,” he says. “We offer complete engines, parts, engine dyno service, and chassis and fabrication services.”

Underneath the 1992 Dodge W250 body of the O’Bryant competition puller is a 2001 frame that’s been sectioned and stretched eight inches to give the truck a longer wheelbase.

And while O’Bryant has helped build a number of title-winning puller trucks over the years, the shop’s own Limited Pro Stock puller is a particular stand-out project for the team. “We run a 1992 Dodge W250, pulling mainly with the Lucas Oil Pro Pulling league series, as well as state-level events with Battle of the Bluegrass,” he explains. “What drew us to the class is the availability of hooks around us, and the competitors. We are pulling with a lot of the same guys that we started pulling with over ten years ago, and we all have a good time together.”

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Since the ’92 body and 2001 frame are from two different generations of Dodge’s full-sized pickup, making the two work together isn’t a plug-and-play operation.

As the name suggests, the Limited Pro Stock class stipulates a few specific limits on the truck’s configuration. “We are limited to 444 cubic inches, OEM frames, steel bodies, D.O.T.-legal tires, and 3.0-inch smooth bore turbocharger, which is the biggest horsepower limiter.” The Dodge’s 1992 body is mounted on a 2001 frame, and in order to maximize the wheelbase, the O’Bryant team sectioned and stretched the bed eight inches.

Powering the W250 is a 6.7-liter Cummins B-Series engine with a 3.0-inch smooth bore turbocharger. While O’Bryant wouldn’t give specifics about the power it’s making, it’s safe to assume this mill is cranking out well over 1,200hp.

The O’Bryant team’s setup also utilizes a 6.7-liter Cummins B-Series engine block that they outfitted with a one-inch steel deck-plate and ductile iron cylinder liners. The driveline consists of a four-disk pedal clutch built by Kenny Smith, an SCS reverser/transfer case combo box, Dana 60 front end and a 20-145 rear end built with parts from Kenny Smith. An RPM Performance logger is used for data acquisition. 

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With class rules stipulating DOT-legal tires, OEM frames and steel bodies, these incredibly capable competition pullers still resemble trucks you’d see out on the road.

“This one is setup with our 60mm roller camshaft, ductile iron recast 12v cylinder head that Wagler Competiton Products has developed with us, and it utilizes a fuel injection and turbo charger system from Harts Diesel and Machine,” he says. “Horsepower is a guarded secret in this class though. With our air limits we all work hard on the dyno to try and get an edge over each other, but I can say that north of 1200hp is required to be competitive. This engine won the Pro Pulling League points championship for us in 2017.” 

O’Bryant says that they completed the truck for the 2016 season and the TS Performance Pull event ended up being the first passes on the truck. “We worked on it until the early morning hours, loaded up drove straight to the pull with no sleep. The truck came straight off the trailer and we took the win.”

O’Bryant tells us that he’s been working with Diamond since the early days of O’Bryant Diesel Service. “Since 2013 we’ve been using Diamond’s custom billet pistons and tool steel pins. By working with them on their billet pistons we are never limited on what we want to try in terms of design. They have built pistons for us for everything from 2500+ horsepower Super Stock trucks to 3000 rpm Limited Hot Farm tractors.”

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And while winning the points championship might be enough for some teams, the O’Bryant team isn’t willing to rest on their laurels. “We are currently building a new engine for the 2018 season,” Patrick says. “That one will utilize a new cylinder head design, pending dyno results.”


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Written by Bradley Iger

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