In each issue of Diesel Power, this Burnin' Rubber department takes a look at the world of diesel drag racing and tractor pulling. This time, we focus on two hard-pulling and rubber-burning vehicles being built for competition.
Christopher Watson's Modified Class-Pulling TruckWhen Christopher Watson isn't out working for the family business, he's probably in the shop cooking up an idea to make his truck pull past the 300-foot line. Chris has been pulling weight transfer sleds across dirt tracks for more than 10 years. Starting out with garden tractors and working his way through the Farm Stock and Hot Farm tractor pulling classes, he's been around the block a time or two. While he was growing up, Chris' father, Paul, pulled 4x4 pickup trucks and garnered nearly 20 years of experience. This helped Chris with his current project, and certainly set the stage for Chris to carry on where his Dad left off-only this time around, they're doing it with diesel pickup trucks.
This '03 Ford F-350 was built for one mission: pulling toward the 300-foot line and beyond. Even though this truck's platform and body are all Ford, the Watson's chose to run a Cummins B-series 5.9L (12-valve) engine. Chris ordered a truckload of parts from Scheid Diesel Service and assembled them on his own. Engine assembly started with an OEM block machined for fire rings and a girdle secured in place. The balanced, reciprocating assembly is an excellent grouping of Arias pistons, OEM marine connecting rods, and the OEM forged crankshaft. The valvetrain is orchestrated by using one of Scheid's custom billet camshafts (with roller lifters). Oversized Inconel valves retained by titanium keepers were fitted into the fully ported head and worked over by an Indy Cylinder Head. The use of Haisley Machine and Repair 14mm head studs and a copper head gasket keep the head planted and sealed to the block, even though there's upward of 180 psi of manifold pressure to contend with. Every last bit of that boost will be needed to burn all the fuel put out by the Bosch P-7100 injection pump and injector nozzles supplied by Scheid.
Speaking of boost, when an engine can be cranked up to the far side of 5,500 rpm, it makes short work of lighting off a very large set of Scheid-spec'd compound twin turbochargers using billet compressor wheels. Exhaust gases are routed from the engine through an ATS manifold that has been port-matched to the turbine housing. Keeping dust out of the engine is left up to a large K&N filter. When conditions allow, a velocity stack is put in its place. If the Cummins were to get out of hand, there's a custom-made guillotine air shutoff valve at the ready.
Cooling the fire within is easy with Scheid's gear-driven water injection system. So, when things get hot, a grand total of 11 nozzles are in use. Nine nozzles begin to spray almost immediately, while two more are set to sequentially actuate once the pyrometers read 1,200 and 1,300 degrees F.
Engine tuning doesn't involve any guesswork with a full-blown Corsa data acquisition system. This truck sports many sensors that provide feedback about such things like boost, EGT, turbine drive pressure, oil/fuel pressures, and charge air temperature. There are a total of 10 pyrometers dedicated to monitoring EGT alone-need we say more? Auto Meter gauges provide traditional analog feedback at a glance as the truck is headed down the track. There's even a SPA boost/EGT gauge thrown in for good measure. Jim Sample, of JR Electricks, wired the truck up to perfection and added a Data Acquisition System.
The Watson's truck is a poster child for stout drivetrains. If you see this truck being pushed or pulled around the pits, there's a very good reason: the fly weighted Crower four-disk clutch doesn't start to grab until around 4,000 rpm. Once the clutch is engaged, the Profab transmission is up next and is equipped with only one forward and reverse gear. To make up for the lack of gear ratios, there's a Profab drop box with quick-swap gearsets. This allows for tuning based on track conditions or sled settings. Custom driveshafts with 1580- and 1410-series joints hang off both ends of the drop box and guide the power into the differentials. The five-linked front axle is a Dana 60 that served well underneath a Dodge before it was stuffed with 6.17:1 gears, an ARB Air Locker, solid U-joints, and 1-3/4-inch axleshafts. Mounted solid to the frame is a 2-1/2-ton Rockwell 106 that keeps its heavy-duty axles locked up tight to the 6.20:1 ring-and-pinion set with a spool. For those keeping score, the numerically lower ratio in the Dana 60 gets the wheel speed up in the front to pull the truck along, instead of the traditional equally biased distribution. Thanks to a set of custom drive hubs, the 10x16 Eagle Alloy wheels bolt right up to the rear axle. Hand-cut 33-inch Mickey Thompson Baja Claw tires do the digging.