Inside The Engines Of The Fastest Piston-Powered Car at Bonneville

We’ve brought you lots of interesting engines in the past, but this one – well two, actually – might be the most interesting, in our collective opinions here at EngineLabs. If you are a fan of land-speed racing, you’re probably already familiar with the recent land speed record broken in Bonneville. For those who don’t follow Bonneville, the unofficial record of the fastest piston-powered car was smashed by Danny Thompson, accomplished racing driver and son of Mickey Thompson.

Thompson accomplished the feat in a twin-engine streamliner (think extremely aerodynamic rail car) named Challenger 2, which his father campaigned as well, years back. Powering the historic vehicle to record-setting speeds are a pair of 499 cubic-inch A/Fuel Hemi engines which individually are awesome, but as a pair are superb.

The Plural of Hemi

Both engines in the vehicle are identically constructed and set up, which makes maintenance a little easier. Essentially A/Fuel dragster engines (think naturally aspirated Top Fuel/Funny Car engines), the Hemis are built by Richard Catton of RC Performance. “Jerry Darien originally gave us the layout of the engine, then my engine guys built it,” Thompson explains.

The base of the engine is a solid aluminum Brad Anderson Enterprises engine block, the same as found in Top Fuel engines. You can also see the Missile external oil pump system and MSD Pro Mag 44 Magneto system.

The engines start off with a Brad Anderson Enterprises (BAE) aluminum dry engine block. From there, a 4.150-inch stroke Sonny Bryant crankshaft is dropped into the Mahle main bearings. Bill Miller forged-aluminum top-fuel connecting rods are bolted to the crank, and then a set of 4.375-inch Bill Miller forged aluminum pistons are attached to the rods. Mahle rings keep all the combustion inside the cylinder, while a Moroso pan and Missile oil pump comprise the dry-sump oiling system, which keeps the engines lubricated.

Moving up top, a set of BAE Fat Head 8 A/Fuel Hemi solid aluminum cylinder heads provide an incredible amount of airflow both into and out of the cylinders and feature dual plugs and 96cc combustion chambers shaped specifically for the burn characteristics of nitromethane. 2.450-inch Manley intake valves and 1.900-inch Manley exhaust valves are controlled by Manley valvesprings, while the BAE rocker system is actuated by Smith Brothers pushrods. The camshafts are a pair of custom identical bumpsticks from Bullet Cams.

The Sonny Bryant crankshaft is a proven component in the drag racing world, and as Thompson points out, he’s just engaged in a really long drag race. This view also happens to be the view the crew gets while inspecting bearings after each run. With the packaging constraints of the streamliner, the team has to go through the oil pan to check the bearings.

The mechanical fuel-injection is a Jerry Darien system with Waterman pumps and Enderle nozzles, and Horsepower Engineering barrel valves, running an 87-percent nitromethane/13-percent methanol fuel mix. Bringing the air into the system is a dual-bore Accufab throttle body mounted to a Hogan sheet-metal intake manifold, while MSD ProMag 44 magneto system keeps the candles lit at well over 400 miles per hour and 7,000-plus rpm.

“We run 68 seconds in an engine with no water. The fuel cools it, so we have to maintain balance between putting cylinders out with too much fuel, and keeping enough fuel to cool everything, and having enough spark to keep all that fuel lit,” says Thompson of the delicate balancing act of tuning the engines.

While the valvesprings aren’t necessarily being taxed through excessive RPM – the engine “only” spins to approximately 7,200 rpm on a run – the huge valves and high load is brutal on them. On both record runs, one engine lost a valvespring, taking out the cylinder.

Two pairs of Jeff Heywood custom headers house the exhaust gas temperature probes used for tuning, and get the spent gasses out of the engine in the most efficient manner possible. While the engines have never been run on a dyno, conservative estimates put them at 2,500-plus horsepower.

We’ve pointed out the similarities in the hardware between Thompson’s engine program and an A/Fuel drag racing program, and the similarities in programs carry into the maintenance program as well.

“We perform the same maintenance as a drag race car. We look at all of the bearings after each run,” Thompson says. “We don’t pull the cylinder heads each time, just because of the way everything has to be packaged in there; it’s way too labor intensive. So we pull the pan every run and go through the bearings. Typically we’ll change one or two bearings per run, but this last week, we changed all the bearings in each motor, just to be safe, since we knew it would be our last run.”

The BAE rocker system is designed specifically for the BAE Fat Head 8 cylinder heads. While the exact ratios are undisclosed, as are the Bullet camshaft specs, they are obviously large. Massive Smith Brothers pushrods are required to withstand the rigors of the valvetrain dynamics in this application.

Choosing the Engines

Originally, Challenger 2 had two engines, but they weren’t twin engines. “My dad, 50 years ago, had an injected motor in front and a blown motor in back, so that he could see out the front of the car,” says Thompson of the streamliner’s original engine configuration. “We wanted to keep the car mostly in the original configuration. We had a box to work within [the existing chassis] and we had already put more stuff in there than would fit. We could have put a blower on it, but we would have had to cut the chassis and lengthen it like two, three, or even four feet to fit everything in there. That would have ruined the integrity of the whole project.”


Danny Thompson walks us through the interesting start-up process of both 499 cubic-inch engines. 

When it came time to start an updated engine program while still running something similar to what his father had run previously, the idea of twin A/Fuel Hemis came up. “We knew that [A/Fuel] engines made a ton of horsepower, and that drag race guys make that power, beating them up every weekend,” Thompson explains. “Although, they only have to do it for four seconds, and we’re doing it for a whole lot more. We’re essentially in a 68-second drag race and they work really well.”

Since a naturally aspirated engine was the only option for the front engine due to packaging and forward-visibility concerns, the team decided that twin engines made the most sense. “These things run so close to each other in their performance, it’s amazing. The first time I read the data, I asked, ‘Am I reading this right?’ I was astonished,” Thompson said, genuinely in wonderment. “I haven’t had a chance to pore through this year’s data yet, but last year the two motors ran within 15 RPM of each other. I don’t know how we pulled that off, but we’ll take it.”

The streamliner design inherently offers some packaging issues, but Challenger 2 is exceptionally tight, as it was designed around technology from 50 years ago, which was generally smaller in size than today’s go-fast equipment, further increasing the difficulty of between-run engine maintenance.

Making Record Runs

Since there are two 499 cubic-inch engines, the displacements are added together for the purposes of classifying Challenger 2 at Bonneville. “’AA’ is anything over 500 inches, and we’re considered to be at 1,000 inches with the two engines,” explains Thompson. “’F’ is Fuel, which designates nitro, and ‘S’ is streamliner.”

Going into 2018’s Speedweek, Danny Thompson held the AA/FS class record at 406 miles per hour, but the team was gunning to significantly increase that record. And they did – significantly. “The two-run average was 448.757 mph,” Thompson reveals. “We bumped our class record by 42 mph. It was 406 and now it’s 448. That’s substantial.”

Additionally, with that 448.757-mph average speed, the team set the unofficial record of the fastest piston-powered vehicle, which previously sat at 439 miles per hour. Most impressive, is that the accomplishment was done naturally aspirated, on fifteen cylinders. “We lost valvesprings on both runs,” Thomson chuckles. “So for both runs, one engine was on seven cylinders. But she still performs.”

Going forward, the Challenger 2 program is officially retired, but the land speed bug isn’t necessarily out of Thompson’s system, especially with the possibility of forced-induction still on the table. “I’d like to do a twin-engine blown fuel car. We’ve got some very rudimentary sketches, but that will all require funding,” Thompson revealed. “I would probably go with a blown combination next time, because the A/Fuel motors are notoriously difficult to stay on top of, tuning wise.”

While only time will tell how long Thompson’s record will stand, you can bet that if it is topped, we’ll do our best to bring you a look at the engine(s) that accomplish that feat. For now, these two naturally aspirated 499 cubic-inch BAE Hemis are the fastest piston engines on the planet…On the ground, at least.

This is a single-pass timeslip for Challenger 2. Once it was backed up on the course the following day, the two Mile 5 speeds were combined and averaged for the official AA/FS record (and unofficial overall piston-powered vehicle record) of 448.757 mph.

About the author

Greg Acosta

Greg has spent over a decade in automotive publishing as Senior Editor of Race Pages magazine. In his free time, he is a firearms instructor and volunteer in the police armory.
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