Imagine a racing program kept so silent that not even motorsport’s most inquiring minds would be able to figure it out. No leaked information, no teasers, no slip-of-the-lip. Dead silence until one month before the biggest racing event of the year. That could never happen in this modern era. But Penske, Ilmor, and Mercedes pulled it off in the early 90s in order to produce one of the most unprecedented Indianapolis 500 entries of all time.

(Welcome back to the , where we all get together to read books about racing and you send in all your spicy hot takes. This month, we’re looking at Beast by Jade Gurss, the story of the top-secret Ilmor-Penske engine that absolutely astonished the world at the 1994 Indianapolis 500.)

It all has to do with a little stipulation in the rules governing the 500. At that time, the oldest race in the world was sanctioned by the United States Auto Club, or USAC. To put it pretty simply, USAC allowed two different engine types to be used in the 500: a purpose-built overhead cam turbocharged V8, or a stock block engine with pushrods and rocker arms. But Roger Penske (now ) noticed that, ahead of the 1994 Indy 500, something had changed. “Stock block” was no longer part of the pushrod engine rules. That meant he, along with Paul Morgan and Mario Illien of Ilmor engines could team up to produce a purpose-built pushrod engine.

And they would do it in less than a year to make sure no one else would get there first.

Most race engines take way longer to develop, produce, and test. We’re talking a nine-month build process before you even get a car on track. And the Ilmor team—who later badged their engines as Mercedes when Penske’s previous engine sponsor, GM, backed out of the deal—managed to pull it off.

Gurss does a damn good job with the information here. He had no hand in the actual production of the engine in question but had heard stories about it from coworkers throughout his career. Anyone who had had even a minor part to play in the project looked back at that time with fondness and possessed a hell of a lot of great stories to share. Gurss decided to take all that information and make it into a book.

He relies on firsthand accounts from countless people involved: chief designer Nigel Bennett, Ilmor designer and engineer Alan Cook, Penske mechanic John Cummiskey, and more. Every single person on the project was sworn to secrecy, unable to even go home and tell their spouse about it. They were expected to put in long hours (some worked for Ilmor’s main Indy engine project during the day, with the surprise Indy engine being tackled once the main employees went home for the night).

Many were fresh college graduates with a passion for motorsport. Most were given a single engine component to design or manufacture. And because everyone was doing it all at once, and on such a tight schedule, there was no guarantee things would actually come together in a way that made sense. It’s fun hearing about those experiences in retrospect—the confusion, anxiety, but overall pleasure at being part of something so important.

The only issue I had with this book was, coincidentally, part of what makes it so great. There are tons of firsthand accounts sliced up and pieced together where necessary. It’s great in that it offers a comprehensive picture of all aspects of the project—but there are so many names that it’s easy to get lost and confused and forget who everyone is. There’s a handy ‘cast of characters’ at the end of the book that I referred to constantly during the four days I took to read the whole book. But I very desperately hate having to take myself out of a fast-flowing narrative to refer to notes or names in the appendix.

Even the technical details didn’t throw me off, and I can go a little glass-eyed when things get too dense. Gurss knows how to write in such a way that you just get it. At one point, he compares the difference between the pushrod and the overhead cam engines as the difference between eating with chopsticks and eating with a fork (i.e. one takes far more balance and skill than the other). His descriptions are clever, ensuring that anyone could pick up this book and have a complete grasp on its contents.

That said, it was one hell of a ride. Gurss’ prose style is madly gripping and emotional, so that it feels like you’re part of it—an impressive feat for a writer who wasn’t even there! When parts of the engine fail at the very last second, I was sitting there holding my breath, a ball of dread in my stomach. When all three Penskes were absolutely killing it in Indy 500 practice, I was hyped enough that I was smiling.