Chain Smokin’ II: A Ground-Pounding IH Packing 1,200hp

• January 12, 2021
• Story By
  Mike McGlothlin

They’re busy tearing through the dirt all across rural America during the summer months and even perform as the headlining act at many venues. They are turbo, fuel and rpm limited, yet somehow, someway, the engines that propel them belt out 1,200hp or more, and they do it in ultra-reliable fashion. They’re called Pro Farm tractors and we had the luxury of getting up close and personal with one over the summer. It’s called Chain Smokin’ II, an IH 966 model campaigned by three generations of farmers: Roger Thompson, his son, Greg Thompson, and Greg’s sons, Hunter and Kutter Thompson.

From its overbuilt DT466 engine to an indestructible transmission to a single turbocharger that produces triple-digit boost, hang on. This wheels-up wonder is chock-full of cutting-edge fuel, air and driveline technology!

33 Years In The Family

Plucked from a southern Missouri junkyard back in 1987, Greg Thompson’s IH 966—a 1974 model—was put to work right away. Not in the fields, but in front of the grand stand. Over the years, the tractor became more and more serious, and Greg eventually made the decision to enter Pro Farm—a category where four-digit horsepower, wheelie bars and tube chassis frames are the norm. Haslag Steel of Washington, Missouri built the tube chassis, wheelie bars and tie bars. In case you were wondering (we were), tie bars keep the transmission housing from breaking in half.

A DT466 With 1,200 HP

The International DT466 is one of the most familiar power plants in all of tractor pulling. Since its release a half century ago, it’s proven itself to be one of the toughest inline-six diesels ever created—so much so that entire tractor classes are based around the use of it. In this case, a 466ci engine is the largest displacement allowed in the Pro Farm rulebook. The version nestled in the Thompson’s tractor is far from stock, however, with a dry block concealing stronger rods and pistons, along with a concrete-filled cylinder head that’s been cut for fire-rings, ported and polished, fitted with larger valves and secured by way of head studs.

100-PSI Of Boost From A Single Turbo

Throughout the world of tractor pulling, a Hart’s turbocharger is one of the most common discoveries you’ll find. To keep pace with the toughest Pro Farm competition, the Thompson’s opted for Hart’s class-specific 3x3-inch charger, complete with a polished velocity stack. The cutting-edge turbo sports a billet compressor wheel with a 76mm (3-inch) inducer, a 76mm turbine wheel (exducer) and produces as much as 100-psi of boost. Because intercoolers aren’t allowed in the primary organization the Thompson’s pull with, a 5-nozzle water-injection system is employed to cool off the incoming compressed air. Greg tells us the tractor’s elaborate water-injection system limits EGT to 1,400 degrees F.

Big Fueling

Like the class’s displacement rule, the Thompson’s are right up against the maximum amount of fueling allowed in Pro Farm as well. While larger, 8000 series Bosch P-pumps aren’t permitted, the Bosch P7100 is. This one was built and benched at Fair Valley Performance in Sauk City, Wisconsin. It benefits from 13mm plungers and barrels and is governed at 3,500 rpm, the maximum engine speed allowed in the class. The 13mm P-pump sends fuel to injectors with triple-feed bodies and that have been equipped with 5x0.027-inch nozzles.

Weighting Up (or Down)

Depending on the organization they’re hooking with or the venue hosting the pull, the Thompson’s tractor competes at either 9,500 pounds or 10,000 pounds. Thanks to IH suitcase weights, weight can be stripped or added in 100-pound increments. It’s worth noting that weight placement on a tractor is very strategic, and can change the outcome of a pull. For this reason, a driver that moves weights around while in line waiting to hook can throw off another competitors’ game plan. We’ve even seen some competitors go to the extent of having fiberglass replica weights made in order to throw off the competition.

Rear Axle & Transmission Upgrades

To eliminate breakage, the cross shaft in the rear differential has been fitted with needle bearings, a common upgrade for higher horsepower pulling tractors. As for the transmission, the factory units tend to break in Pro Farm, so the Thompson’s avoided this weak link by installing an Atlasmax Component transmission from Atlas Tractor. A 3-disc Crower clutch transfers power from the engine into the aftermarket transmission. With 20.8-inch rear radial tires sporting hard-biting, ½-inch deep cuts (and combined with 1,200 hp), these reinforcement measures were more than necessary.

The Race-Ready Cockpit

As with any motorsport, safety is a top priority, hence the roll cage that surrounds the driver and the 5-point racing harness that secures him within it. Also notice the long foot brake pedal. A second one exists on the other side of the tractor. The right and left brakes are used to steer the tractor when the front tires are air born, which is the case for most of the track. ”Hopefully you never have to touch them, though,” Greg tells us. “It’s a speed game and you lose ground real fast when you use the brake.”

Storming The Track

So what’s it like to drive this beast? With 1,200 hp, 100-psi of boost and the front wheels off the ground most of the way down the track, it’s loud, it’s fast and it’s fun. “Our fastest gear is 32 mph,” Greg told us. Trust us, that’s a pretty fast ground speed to achieve in truck and tractor pulling. “It’s a rush,” he went on. “When the weight hits the pan on the sled it pulls that 5-point harness hard and forces you back in the seat.” Although the Thompson’s were forced to run a limited pulling schedule in 2020, Greg did manage a hard-earned Second Place finish at an ITPA hook against 10 other Pro Farms.

A Family Affair

With Greg, his father Roger and his son’s, Hunter and Kutter, all taking turns driving, tractor pulling is definitely a family affair for the Thompsons. Not only are the driving duties split between the four of them, but the events they attend are split between two pulling organizations: the Illinois Tractor Pulling Association (ITPA) and the United Pullers of America (UPA). For Greg, having his sons get behind the wheel allows them to partake in the sport that’s been his father’s pastime of choice for more than 50 years. “My dad got started pulling with an IH 560 back in the 1960s—when you had to step on the sled as it went by,” he told us. Like a lot of families in tractor pulling, the sport has been passed down to each generation.