Thanks to a pro tip from Micah over at Off Road Xtreme (yes, two Micahs under one umbrella… go figure) we were able to gain access to a YouTube video focusing on the engine that powered Luke McMillin’s #83 Baja-winning AWD trophy trophy truck.
Piloted by the youngest member of the McMillin Racing Team, the off-road racing prodigy dominated all 828 miles of the Mexican desert, securing the #83 SCORE trophy truck’s title as the 2022 top-running vehicle.
In the video’s intro, you will see the battle-scarred trophy truck, shipped in straight from the dusty dunes of Baja. What you won’t see, is the 555 cubic-inch big-block Chevy engine that propelled McMillin to one hard-earned victory after another. That part comes later…
As you will see, Troy from Maxima Racing Oils met up with Kevin Kroyer of Kroyer Racing Engines after the event was over, to see how the 555 cubic-inch big-block Chevy held up. Luke’s winning time was an impressive 16 hours, 37 minutes. Even more impressive was the configuration that made it all achievable.
This big-block came paired with a 5-speed Xtrac Ltd transmission and was simultaneously installed within the caged confines of a one-off creation by none other than Mason Motorsports. A trophy trophy truck producing powerhouse and fantastic fabricator, that saw all three of its trophy trucks win all three Trophy trophy truck class championships in SCORE’s 2022 season, with the 2023 season securing even more wins for the trophy truck builder.
Making A Bigger, Faster, And More Reliable Trophy Truck
Since the video does not divulge a lot of information on what all this big-block comes loaded with, we decided to do a little digging, to see what aftermarket modifications have been made to this monster.
This proved a bit more challenging than expected. From their websites to social media accounts, Kroyer Racing Engines, McMillin Racing, and vehicle builder, Mason Motorsports provided little written explanation as to what this combination contained. It was not until we came across a PRI Magazine interview, that some concrete details on what makes this repeated race-winning engine work. And it has just as much to do with traction and transmissions as it does with big-block brawn.
Over the last few years, the all-wheel-drive technology has shown up big in our sport where it was traditionally two-wheel drive and typically a small-block because you couldn’t get a lot of traction. Now it’s all-wheel drive and big-block-based engine packages… They’re more the norm now. — Kevin Kroyer, Kroyer Racing Engines
Within the interview side, the discussion of how the switch from RWD to AWD has brought with it a substantial bump in performance and power. Fully built big blocks and Joe Gibbs engines are the two go-to options, with 1,100-plus horsepower being the norm nowadays.
However, Kevin Kroyer, who built the race-winning motor in the McMillin #83 trophy truck, feels that Kroyer Racing Engines doesn’t need all that. “I don’t make anywhere near the numbers that everybody in California makes,” Kroyer told PRI Magazine. “Everybody else is advertising 1,100, 1,200, 1,300, whatever. As long as we can pass you, we’re okay.”
Kroyer explains that since big-blocks have been around for so damn long, constructing one of these motors based upon winning aftermarket combos in endurance boat racing is the closest thing you’ll find outside of Baja. “There are some similarities there,” says Kroyer. “But we’re trying to push 7,000-pound trophy trucks with all-wheel drive and 30-some-odd inches of wheel travel for up to 24 hours. So they gotta run pretty hard, but they also gotta be reliable.”
Now as for Kroyer’s winning combo of aftermarket enhancements, it all starts with a base blueprint of an aftermarket Brodix aluminum GM-style block, with a short deck that’s been custom-machined in-house. Machined down to size, the 555-cubic-inch bottom end is then filled with a Bryant billet crankshaft, Carrillo rods, and JE pistons. From there, Kroyer adds a Daley Engineering dry sump setup with an integrated pan and pump, along with a front engine plate and drive accessories from ID Designs.
Topping off the combination are a set of Dart 20-degree heads and mechanical roller camshaft, T&D rockers, and a proprietary Kroyer cam drive design. As for air induction, that is typically an ITB throttle-body system courtesy of Kinsler; complete with drive-by-wire configurations, and MoTeC control from top to bottom.
Post-Race Autopsy Says?
So how did the engine fare, you ask? All things considered… pretty damn well. While the wear on the ends of each bearing was likely the result of some crankshaft flex rub, the main bearings and pistons were far more fascinating to see up close.
In the video, it appears that the main bearings only had a few hairline scratches embedded in them. As Troy is quick to point out, and Kevin Kroyer concurs, this is more than likely due to the brutal, dusty environment that the trophy truck was just submitted to for an unholy amount of time. That massive, ITB-stacked air filter may be engineered to keep dust particles out, but when you are surrounded by the silty stuff for more than a day, a certain amount of it will inevitably make its way into the motor.
Now as for those products from JE Pistons, it seems that the undercrown portions of all eight piston heads were in immaculate condition, and only showed minor wear. Unlike what you often see on endurance race engines, the pistons had not “cooked” the oil, which is pretty wild considering that Kroyer Racing Engines does not implement piston squirters in the #83 trophy truck’s engine.
The wrist pins all seemed fine as well, and there was no sign of galling anywhere on the pin bores or along the rod bushings, where you will often see damage after such extreme levels of sustained abuse.
Upper-end-wise, all of the pushrod tips appeared immaculate, and the same could be said for the rocker end of the head. Hell, even the engine’s adjuster screws, which are known for occasionally crapping out under pressure when the heat is on looked brand new.
Reconstruction And Further Lubrication Required
After being fully disassembled and inspected by Kevin Kroyer and the team over at Maxima Racing Oils, it became apparent that very little (if anything) was wrong with the #83 trophy truck’s powerplant. So the guys reassembled the engine and put it back on the dyno for recalibration prior to going back into the chassis. This time around they used Maxima’s Performance Break-In Mineral Engine Oil, before switching back over to regular race oil in the trophy truck.
As the chief liquid and lubrication sponsor, the #83 trophy truck’s motor continues to be run exclusively on RS1550 high-performance synthetic motor oil from Maxima Racing Oils. According to the company website, this 15W-50 liquid has been engineered exclusively with flat tappet camshafts in mind and comes packed with double the zinc as a normal synthetic race oil.
Apparently, this oil is further reinforced with specialized esters and polymers that are intended to help negate the risks associated with endurance racing. This makes complete sense, especially when McMillin’s RPM figures can be seen spiking well past 7,000 rpm in the straights, only to drop to 2,500 rpm at the next bend, before being sent soaring all over again. All in 100-plus-degree Fahrenheit heat, for 12 to 24 hours on average… nonstop.