8up Mud Truck
Anyone who has spent a good part of his or her life competing in anything from football to mud racing has met a guy like this. The guy with the brand-new badass gear and truck that strolls into most events just in time or maybe a few minutes late. He brings the loudest toys with the brightest colors to take on the best competition in the nation. As he arrives and cruises through the gates, people stop what they are doing and stare in awe, even your girl. He unloads his rig, preps it at the starting line, and tears through the track to take the gold. Then, after the race, he sits back, relaxes, and gets 8up with you and all your buddies. The guy is so cool and always makes it look so easy. Well, Robby Armstrong from Sarasota, Florida, is happy to be that man. An ’04 Chevy Silverado is his gear, and his area of competition is in the mud!
Sure, Robby won’t win every race, although when he loses you can guarantee that truck will need to be fixed before it can race again. He doesn’t go light on the throttle, and he won’t back down from any jump. You have to have a lot of confidence to race the way Robby does, and as long as Mike Trotter from Mims, Florida, is the lead builder on his rig, confidence will not be an issue.
Using the knowledge they picked up from building and racing his first 8up truck, Robby and Trotter used 1 3/4-inch mild steel DOM tubing to build the frame strong and lightweight. Robby went with an Ouverson 103 front axle, and a 106 rear axle. Both axles have a gear ratio of 620 and are locked up. A set of 1410 U-joints, an SCS gearbox with a 1.59:1 low-range ratio, and a J&W Turbo 400 transmission all work together to propel this machine to the finish line. The crew also installed a Driveline front and rear brake kit with a Wilwood master cylinder to make sure 8up will stop when told to. Robby also had a manual transmission brake installed for additional stopping power and safety.
The suspension consists of four-links and 18-inch King coilovers shocks that have no problem keeping this rig under control on the toughest terrain or in the deepest part of the course. Staying on the track at high speeds is possible thanks to a custom hydraulic steering box and a TXT steering stabilizer. A set of custom-cut 8up 24-inch wheels were built with a 5 inches of backspacing up front and 3 1/2 inches in the rear. BKT supplied the six-ply 14.9x24 R2 tires that sling the Florida mud.
When it came to power, Robby had a few new ideas in mind. One of the most noticeable modifications to this intense rig is the rear-mounted 572ci Dart Big M Block that has been balanced and blueprinted by Central Florida Machine in Winter Garden. Added were J.E. Pistons with an 8.5:1 gear ratio, a Callies crank, A.F.R. aluminum heads, Zommies 2 1/4-inch headers, and a Littlefield 1471 Hi Helix blower. To give it additional power and performance, the big-block motor was converted to run solely on Alcoho0. After a few last touches (including an MSD ignition), this motor was tested and dyno’d at around 2,000 hp.
Leaving the interior simple and to the point, Trotter bolted in an aluminum Kirkey Racing seat, a fully welded custom rollcage, and Auto Meter gauges to monitor the vitals of this monster. Dave Eldridge from Eldridge Body Shop in Sarasota covered the fiberglass Chevy Silverado body in PPG “O So Orange” paint, and they threw on a few 8up decals so you would remember the name.
You can watch Robby and crew race this amazing build at almost any Mega Truck Bad Boys event in the country. (See the Mega Truck story in this issue for information on the racing circuit.) Robby would like to thank all the amazing and talented individuals who helped with this build. Stop by and talk racing if you see them at the track. Sometimes the guys with the nicest toys are nicer then the toys they have.
2004 Chevy Silverado
Owner: Robby Armstrong, Sarasota, Fla.
Engine: 572ci Chevrolet Dart Big M Block, rear mount
Transmission: J&W Turbo 400
Transfer Case: SCS, 1.59:1 low-range ratio
Axles: Ouverson 103 front axle, 106 rear axle, 620 gear ratio
Shocks: 18-inch King coilovers front and rear
Tires & Wheels: Custom cut 8up 24-inch wheels, BKT 6-ply 14.9x24 R2 tires