How Reliable Are Proline HEMI Engines? Here's What Owners Have To Say

Proline Racing (PLR), not to be confused with Pro-Line Racing (an RC car parts supplier), builds some of the most renowned drag racing powerplants on the market today. If you watch something like Pro Mod or Outlaw cars, chances are you've seen a Proline Hemi in action at least once. The company produces bespoke crate motors in both turbocharged and supercharged configurations specifically tailored for high-horsepower drag racing applications – how high, exactly? Try over 5,000 horsepower. Now that number sounds like a lot (and it is), but it doesn't even touch some of the most savage drag racing engines: the Top-Fuel powerplants, running on exotic fuel like 90% nitromethane, which produce numbers exceeding 10,000 horsepower.

That's quite an important number because often-times the challenge in building these engines isn't producing something with huge power. It's making that power reliable enough that the engine won't just explode the second you go full-throttle. That happens somewhat frequently on these ridiculously-powerful dragsters, enough that they actually wrap components in Kevlar to keep them contained. Which begs one important question: exactly how reliable is something like a Proline Hemi? Yes, it produces half the power, but surely the engines still frequently detonate, right? Well, yes and no.

According to teams and testimonials, the engines are actually extremely durable, with some blocks lasting for years – and they produce that 5,000+ figure with room to spare. Like owner Paul Mouhayet regarding his twin-turbo Hemi: "It'll probably make another five pounds of boost at the track," after recording 5,362 horsepower on the dyno and breaking the company record. Let's take a look at their internals and what other racers and organizations have to say.

Drag racing engines are largely unique in that they only operate at full-throttle for a few seconds at a time, unlike most car engines. But in those few seconds, the inside of a drag racing engine is one of the most violent places in the universe – so the concept of "reliability" takes on a different meaning to what we're used to. These engines frequently break parts and require teardowns, with "reliability" measured more in the block's longevity than the time between rebuilds. For instance, "Every 20 runs or so, we gotta change the [connecting] rods," says famous YouTuber Cleetus McFarland, during a dyno test with his Hemi.

Complete teardowns like these are fundamentally a part of drag racing in general, deriving just as much from safety as tuning and accounting for parts-wear. The highest-level engines often require rebuilds after every single pass to replace critical components because that much power going through an engine no larger than 500 cubic-inch stretches the boundaries of material science to within an inch of its life. However, the Proline Hemi only produces half the power of these monsters and features far less restrictions which hamper reliability. Hence, a Proline is comfortably able to operate on multiple passes without needing any significant rebuilds.

These blocks are built out of a solid chunk of aluminum, emphasizing long-term durability of the block itself. So while the parts inside may break, generally the block housing those parts stays together. Generally their weakest link is the valvetrain, thanks to the Hemi's more rev-happy design over Proline's 481X with its Chevy-style upper. But this is a serious drag racing engine, built for serious applications only – not daily-driving. And in that function, a Proline is among the best: here's what drivers have to say.

PLR Hemis powered various record-breaking vehicles since the company's debut, most recently entering the spotlight as the powerplant in the Murder Nova, an engine it used in dozens of passes since its installation. The Hemi was originally from another record-breaking dragster, Ryan Martin's gray "Fireball" ZL1 Camaro, but with all-new components and in zero-run condition. This engine was rebuilt by Proline themselves, according to Murder Nova owner Shawn Ellington in this discussion from August 2022, and recently went on-sale again in January 2025. So this engine has seen the inside of two potent and frequently-used dragsters, each with well-documented stories and dozens of recorded passes – and it's still going.

The company sports a long history with a reputation for reliability and exceptional tuning ability, according to various forums and articles dating back over a decade. However, several cite the Proline 481X, PLR's sister offering to the Hemi, as being the more reliable option thanks to its big block Chevy-style head profile. That said, PLR prides itself on its customer testimonials, claiming in one interview that they still have units in owners' hands after seven years – incredible longevity considering the forces at-play inside these engines. Further, the Hemi's resale typically exceeding the price of a top-level Ford F-150, despite the blocks having multiple passes, speaks volumes about their longevity. In Shawn Ellington's words regarding his latest Hemi build, "We put 30 passes on it... I keep an eye on the valvetrain, every pass I take it apart, inspect rocker arms, adjusters, pushrods, valve springs... Everything's been good." Is it the most reliable, that's hard to say – after all, there's stiff competition out there. But the general consensus is that Proline are among the best, reliability included.