Sure, everyone loves a 426 Hemi.

350 Chevy? Yep, found dang-near everywhere.

And even non-Ford folks can appreciate a nicely tuned Windsor.

…But there are plenty of other engines out there, reliably powering classic cruisers, work trucks, and humble people movers—just without the panache and fanfare of those more popular powerplants.

So on its social media pages, Summit Racing asked you to fill in the blank:

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“The most underrated engine of all time is _______.”

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The Reader Contributions poured in by the hundreds. We collected ten of the most under-the-radar engines from those responses, and here’s what we came up with. (Spoiler alert: You certainly like your inline sixes!)

Please note, sometimes folks gave us a specific engine, others gave the entire engine family, so we used both interchangeably here.

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10. Volkswagen Air-Cooled Boxer Four

With the right mix of parts, the VW four can be quite potent. See more of this engine (and the Baja Bug it’s attached to) in this Lot Shots feature. (Image/OnAllCylinders)

While this family of engines can be found in millions of vehicles, a lot of folks don’t realize that it has some bona fide performance potential. “You can do a lot to these engines” says Mike L. Then Eddie B. reveals some specifics, like “bored and stroked and turbocharged.”

They’re easy to work on too. “My mom rebuilt one of these on the kitchen table and installed it herself,” Kane D. explains.

Volkswagen-derived fours wound their way into plenty of vehicles, including boats, trikes, aircraft, and even a few Porsche models. These engines are delightfully simple, relatively reliable, and affordable. What’s not to like here?

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9. Pontiac Iron Duke/Tech IV

Our pal Brian Lohnes found this Iron Duke in a clean 1984 Camaro. (Image/Bangshift)

If Rodney Dangerfield was an engine, he’d be the 2.5L Iron Duke. In stock trim, the Iron Duke was loud, buzzy, and not that powerful—but that sucker would run forever with minimal maintenance. Trent P. pointed that out too. “None of them were powerhouses, but still darn good reliable engines.”

Though made by Pontiac, the Iron Duke found itself in a mystifying array of vehicles, from Postal Jeeps to Camaros, Fieros to S-10s, and seemingly every 1980s economy car in GM’s stable.

But despite those pedestrian applications, some readers were quick to point out that the 2.5L four-banger had some potential too. “I’ve seen a few that have been turbocharged and lay down some crazy numbers,” Chris C. tells us. Indeed, the Iron Duke was the Swan Song for Pontiac’s legendary Super Duty engine lineup, and used in plenty of ARCA and IMSA racers.

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8. Oldsmobile V8

You could find an Olds V8 in everything from station wagons to Trans Ams. (Image/OnAllCylinders)

A lot of commenters offered up the various iterations of Oldsmobile’s second-gen V8, like the short deck 350 and the tall deck 455. Heck, Robert P. even tossed the Olds 260 into the conversation. From brute power to gas-sipping efficiency, the Oldsmobile V8 wore a lot of hats around the halls of GM and it picked up plenty of fans along the way.

The engine took to performance upgrades well, and Ulises M. proved that. “My little iron-headed 350, bored .030 over, lays down 11.6s on pump gas.” (Oh, and let’s not forget that Oldsmobile helped carry Pontiac’s performance mantle in the 1970s, either.)

Reader Marco M. mentioned the ill-fated Oldsmobile 350 diesel—but we’re pretty sure he was joking. (Marco, please tell us you’re joking!)

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7. AMC 232/258 Inline Six

Despite its off-road reputation, the peppy 258 was also dropped in AMC’s performance cars like the Javelin and Hornet. (Image/OnAllCylinders)

Sometimes an engine is underrated simply due to the shadow cast by its successor. Case in point: the carbureted AMC 232/258 (3.8/4.2L) inline sixes. While there’s no question that the Jeep 4.0L is one of the best off-road engines ever made, many folks don’t realize that the EFI 4.0L actually evolved out of an inline six originally designed to power AMC passenger cars. Once AMC bought Jeep though, the sixes wound up in the CJ and the rest, as they say, is history.

In fact, that’s the first thing Juan S. points out. “In production 42 years—so good that Chrysler used it until 2006.” Then, John H. chimes in with “it comes with 7 main bearings,” alluding to its durability. Finally, Kent A. quips “had one in a Jeep and loved it.”

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6. GM 4.3L V6

Terry sent us a picture of the 4.3L V6 he’s currently working on too. (Image/Facebook – Terry H.)

What would happen if you took away cylinders #3 and #6 from the trusty small block Chevy V8? Well, you’d get a new family of super-durable 90 degree V6 engines that culminated in a 4.3L six that propelled plenty of cars and trucks in the GM portfolio. Randall F. says “I’ve always had great experiences with 4.3L V6 GM motor,” and Allen M. follows up with “not a powerhouse, but boy they will last forever.”

Nicknamed the “3/4 350,” the 4.3L version shared much with the SBC it was based off of, including some valvetrain parts, bellhousing bolt pattern, and a 4 × 3.48 inch bore and stroke. (Just don’t confuse the GM 4.3L V6 with the “Baby LT1” LT4 V8.)

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5. Pontiac OHC Sprint Six

The short-lived OHC six could be found in Pontiac’s mid-size Tempest/Le Mans and Firebird models. (Image/OnAllCylinders)

So far, most of the engines on this list were just ordinary powerplants that did their jobs really, really well. The Pontiac Sprint 6 is an entirely different story.

Using revolutionary (for the era) overhead camshaft architecture, the Sprint Sixes could’ve been a legit replacement for V8 power. Though thanks to cheap, plentiful gas in the 1960s, the innovative design became a classic case of being too far ahead of its time. Stephen F. nominated this one, and quite a few folks agreed. Plenty of others commented on the Sprint’s rev-happy personality and signature exhaust note.

Want to learn more? We wrote an entire article on the Sprint 6.

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4. Studebaker V8

Here’s a supercharged R-2 Studebaker 289 we spotted in a Lark Wagonaire. Read the whole story on that ‘Stude here. (Image/OnAllCylinders)

“Overbuilt like a tank,” explains Michael H. and Dee I. chimed in with “as tough as they come.”

It’s easy to see why too. Launched in 1951, Studebaker V8s featured forged internals, a gear-driven cam, solid lifters, and 18—count ’em—18 cylinder head bolts. So it’s no surprise that these engines took to forced induction so well, usually by way of a Paxton supercharger. In fact, in super rare “R-3” performance spec it easily made over 300 horsepower. We sat down with known Studebaker expert Malcolm Berry in an episode of the OnAllCylinders podcast and he told us plenty about these engines.

Maybe though, the ‘Stude V8 is better summed up by another commenter, Austin B., who simply said “Studebaker is all around an unsung hero in the car enthusiast community.”

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3. Briggs & Stratton L-Head

Eric included a picture of his vintage Briggs & Stratton engine. (Image/Facebook – Eric F.)

“There are millions of those out there,” Adrian M. says—and we believe him. The humble pull-start Briggs & Stratton powered untold numbers of lawn mowers, rototillers, and snow throwers. (In fact, Jeff M. boasts that he’s “still got 4 or 5 laying around.”)

But it’s their adapted use in minibikes and go-carts that makes these little four-stroke thumpers so endearing. In fact, Briggs & Stratton now offers a lineup of crate engines for go-carts and Jr. Dragsters that’ll keep you from pillaging your neighbors’ lawn equipment.

But perhaps Nate D. said it best, when he proudly stated “this little engine is what sparked my interest in combustion engines and hot rodding!”

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2. Mopar 225 Slant Six

We’ll take any opportunity to mention a Dodge Aspen. (Image/Summit Racing – Jason Liss)

Behold Mopar’s “Leaning Tower of Power.”

While the Slant 6 is easily overshadowed by any number of Chrysler V8s, it is nonetheless a huge part of Mopar history. Like many of the engines on this list, it persevered for decades, adapting to the changing times through fuel injection and evolving emission control systems. And it earned plenty of supporters in the process. “It’ll run forever,” explains Alfred B., while William H. tells us that it is “bulletproof and makes great power.”

In fact, the folks at Engine Power practically doubled a 1971 Slant Six’s output, you can read about that project here.

Yet Pat S. has a bit more pragmatic take on the Slant Six. “A little beast. Gutless but they just don’t die.” 

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1. Ford 300 Inline Six

The folks at Powernation’s Engine Power have done a few high performance builds using the venerable Ford 300 I6. (Image/Summit Racing)

Honestly, we hesitated to include this one. After all, it’s pretty much beloved by the Blue Oval brigade.

Yet at the same time, the 300 doesn’t have the pizazz of a 302, side-oiler 427, or even a Mod Motor. But the sheer overwhelming response the Summit Racing folks got for this one demanded that we not only include the 300—we had to lock it in at Number 1 on this list.

So rather than us prattle on about the 300’s virtues, we’ll let a few of the readers give you the skinny:

  • “The best motor Ford ever built.” – Keith F.
  • “Ran forever and was used everywhere.” – Mark K.
  • “Tough as nails.” – Joe M.
  • “Great engine.” – Bob M.
  • “A true workhorse.” – Robert C.

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Admittedly, there were a ton of great engines that didn’t make the top 10 here, but they have legions of fans nonetheless. So, which ones did we miss? Any glaring omissions on the most underrated engines here? Let us know in the comments section below.

Author: Paul Sakalas

Paul is the editor of OnAllCylinders. When he's not writing, you'll probably find him fixing oil leaks in a Jeep CJ-5 or watching a 1972 Corvette overheat. An avid motorcyclist, he spends the rest of his time synchronizing carburetors and cleaning chain lube off his left pant leg.