Boss 429 HP vs Hemi: A Classic Muscle Car Showdown

Welcome back to Clash of the Classics. This month, we revisit two titans of the muscle car era: the 1970 Ford Mustang Boss 429 and the 1970 Dodge Hemi Challenger. 1970 was a notable year, marked by significant events here in the United States, including the Kent State shooting incident headlining newspapers, music fans mourning the Beatles’ breakup, and on January 11th, the Kansas City Chiefs upsetting the Minnesota Vikings 23-7 in Super Bowl IV.

In the automotive world, however, things were considerably brighter. The 1970 pony car market was at its peak, and both Ford and Dodge were determined to capitalize on their divisional models. Ford, the pioneer of the segment with the Mustang, had dominated throughout the mid to late 60s like no other manufacturer. The folks at Dodge were eager to claim their stake.

Dodge’s powerful response to the Ford Mustang was aptly named the “Challenger.” While it could be argued that they arrived somewhat late to the party, one thing remains certain: it was indeed “Late but worth the wait.”

Let’s begin with a look at the ’70 Mustang Boss 429.

Affectionately known as the Boss 9, the original series Boss 429s are among the most highly sought-after vehicles in the classic car world. With a strictly limited production run of only two years (1969 and 1970), it’s estimated that a total of just 1359 original Boss 429s were ever produced. The value of models like the 69 boss 429 remains incredibly high today.

The Mighty 1970 Mustang Boss 429

The car’s development was driven by a singular goal: to challenge the formidable Chrysler 426 Hemi in NASCAR’s Grand National Division. Ford decided to leverage the Mustang platform, but it required an entirely new engine design. While the 427 and 428 series engines had been successful, they were somewhat aging. The new 429 was fresh and specifically engineered to be the answer to Chrysler’s dominant 426 Hemi. However, to qualify the engine for NASCAR track use, Ford first had to homologate a minimum number by installing them into regular production cars. This necessity gave birth to the street versions of the Boss 429 Mustangs.

Because Ford’s powertrain division was already heavily committed to other projects at the time, the complex development and production of the Boss 429 Mustang was outsourced to a company called Kar Kraft in Brighton, Michigan. To say they faced significant obstacles would be an understatement. For starters, the massive 429 engine simply did not fit into the standard Mustang engine bay as it was over 2 inches too wide.

Kar Kraft engineers were forced to extensively modify the chassis, pushing the suspension outward by roughly an inch on each side. This necessitated a complete redesign of the shock towers and required new, heavy-duty front springs along with redesigned upper and lower suspension arms. Even the brake booster had to be re-engineered or relocated to clear the huge valve covers of the 429. The rear suspension also saw a redesign, featuring a massive rear stabilizer bar, heavy-duty springs, and staggered shocks to help manage the power. Due to these extensive modifications, the car’s overall profile was considerably lower than a standard Mustang. A new design front spoiler was incorporated specifically to preserve adequate ground clearance.

1970 Ford Mustang Boss 429 classic muscle car profile

The Legendary 429 Engine and Boss 429 HP

The heart of this beast, the new 429 engine, featured large alloy hemi-style cylinder heads equipped with massive 2.3-inch intake valves, robust four-bolt main caps, and a forged steel crank for durability. It utilized a unique hemispherical “crescent” type combustion chamber design that bore more resemblance to the traditional Hemi engine used by its rival, Dodge, than Ford’s previous designs.

The official boss 429 hp rating listed by Ford was 375 horsepower, with torque rated at 450 lb-ft. However, these numbers were widely considered conservative. It was common practice back then for manufacturers to intentionally minimize horsepower ratings, largely for insurance purposes, to make these high-performance cars appear less extreme. A more realistic horsepower rating for the Boss 429 was likely closer to 475 hp. The engine was typically paired with a rugged 4-speed top-loader manual transmission, sending power to a 3:91 posi rear differential.

Powerful Boss 429 engine with 429 hp rating in a 1970 Mustang

The original prototypes underwent extensive and rigorous testing, with no detail left overlooked. Not only were there emissions tests that had to be passed according to regulatory requirements, but a battery of environmental tests was also conducted to determine the integrity and performance of the powertrain under a wide range of driving conditions. This entire development process resulted in one of the most refined vehicles of its time, leading some enthusiasts and historians to even argue the car was “over-refined” given its race-bred origins. Ford management approved every design change made by Kar Kraft and greenlit the car for production. Unfortunately, it was a short-lived run, and by 1971, both the Boss 429 and the higher-revving Boss 302 were replaced by the Boss 351. Information about models from the following year, like the 71 boss mustang, highlights this transition. For collectors interested in the rarity and variations, finding a 1969 mercury cougar eliminator boss 429 for sale can also be a challenging but rewarding pursuit.

Up until just a few years ago, I hadn’t had the rare opportunity to personally experience a true original Mustang Boss 429. That all changed when our team at “Horsepower for an Hour” was hosting the Fabulous Fords Forever event in Southern California. John Force, the legendary drag racer, was our celebrity guest that year. After we finished interviewing him and his team, we set out specifically to find a true Boss 429 on display. Of the roughly 480 Mustangs in attendance that year, only one true factory Boss 429 Mustang made it to the show. After a quick and enthusiastic discussion with the car’s owner, we were incredibly fortunate to be invited to take it for a drive.

Nothing can truly prepare you for the experience of driving such an iconic machine; it is almost surreal. The car was pristinely preserved and handled remarkably well, especially considering its age and the extensive modifications made. We found ourselves cruising along Beach Blvd in Buena Park, California, feeling invigorated and genuinely transported back in time. The acceleration was deeply impressive, particularly the raw power available from the 429 engine, as was the entire overall feel and connection to the road. It was undoubtedly a highlight reel moment for me, one for which I’ll be eternally grateful. Discussions around metrics like mustang boss 429 price in india reflect the global interest and high value placed on these rare vehicles today.

Let’s look briefly now at the competing model, the ‘70 Challenger Hemi R/T.

Enter the Challenger: Dodge’s Hemi Powerhouse

The 1970 R/T Hemi Challenger is arguably one of the most iconic and valuable classic cars we’ve ever showcased here at Clash of the Classics. As we discussed earlier, Dodge entered the pony car market considerably later than Ford, but with the introduction of the R/T Challenger powered by the legendary 426 Hemi, they certainly made their entrance count and proved it was worth the wait.

First appearing in the Fall of 1969 as a 1970 model, the all-new Challenger made its highly anticipated debut alongside a newly redesigned Plymouth ‘Cuda. The introduction of these two E-body cars made it unequivocally clear that Mopar (Chrysler, Dodge, Plymouth) was a serious and potent contender in the pony car market. Prior to the release of these specific models, Dodge had already established a significant impact in the broader muscle car market with iconic designs like the Charger, Super Bee, and Coronet R/T. Now, they were strategically positioned to make a direct run at market leaders like the Mustang and Camaro, including rivals like the yenko camaro hp.

One clear and undeniable advantage Dodge possessed was a monster powerplant readily available under the hood. The 426 Hemi engine boasts a long and storied history dating all the way back to 1951, but the engine most of us think of when discussing the muscle car era was the redesigned version first released in 1964, initially for racing use.

1970 Dodge Hemi Challenger R/T classic pony car stance

It is possibly the single most iconic and legendary engine ever produced during the muscle car era. Earning the deep respect of even the most loyal Ford and Chevy enthusiasts, this engine set what would become the benchmark by which all other big blocks would be measured for years to come. Whether dominating on the street or on the race track, the 426 Hemi engine reigned supreme throughout the 1960s and into the early 1970s.

The engine found in showroom models of the 1970 Challenger R/T was officially rated by Dodge at 425 horsepower with just under 500 lb-ft of torque. However, much like the Boss 429, these figures were likely understated. Some independent tests performed at the time pushed the horsepower numbers closer to 435 hp with a torque rating reaching up to 515 lb-ft. Either way, the engine was an engineering marvel, delivering brutal and instantaneous power.

Nicknamed the “Elephant Engine” by enthusiasts due to its sheer size and power, it famously filled the engine bay of the new Challenger. Adding to its already impressive visual presence and performance were a pair of four-barrel Carter AFB carburetors, mounted atop the engine, that served to feed copious amounts of fuel and air to the beastly Hemi V8.

Transmission options for the 1970 Hemi Challenger R/T included either the robust 4-speed manual A833 or the highly regarded Torqueflite 727 automatic transmission. Handling all that prodigious power at the rear of the car, typically, was an Auburn 9.75-inch limited-slip differential equipped with 3.55 gears, providing excellent traction. Dodge also offered a more aggressive 3.90 gearset, although it was seldom ordered by customers. One of my favorite design features of the Challenger R/T models was the shaker hood. I’ve always favored that distinctive style and functional look on a street performance car, but for some reason, Dodge discontinued it after the 1970 model year. Presumably, the reasons were practical, likely having to do with cost containment and potential problems associated with owners driving in colder and wetter climates, where snow or rain could enter through the hood scoop.

Massive 426 Hemi Elephant Engine in a 1970 Dodge Challenger

Underneath the car, the suspension setup was adequate for the time, but like most cars of the ‘60s and ‘70s era, it had inherent limitations at higher speeds or during aggressive cornering due to the prevailing design philosophies. The R/T models did benefit from the inclusion of a heavy-duty stabilizer bar and heavy-duty shocks up front, and the increased spring rate at the rear suspension helped to further stabilize the car under acceleration and braking. Still, overall, the suspension was arguably the area of the car that was most in need of further refinement compared to the powertrain.

Inside, the car was well-designed and thoughtfully developed for its target audience. The optional Rallye instrument cluster, in particular, had a track-influenced layout featuring a 150 mph speedometer, individual analog gauges for critical functions, and an 8,000 rpm tachometer. The steering column design was also quite interesting and unique, as a specially designed cover was added to it that gave the driver’s cockpit a distinct, almost fighter jet-like feel.

Interior view of the 1970 Dodge Challenger R/T Rallye instrument cluster

It is estimated that Dodge produced a total of 18,500 Challenger R/T models in 1970 across various engine options. Of those produced, only a very limited number were equipped with the potent 426 Hemi engine – an estimated 356 cars in total. This breakdown included 287 hardtop models and an exceptionally rare 69 convertible models. It is currently unknown how many of those original Hemi cars survive today, but a concours level convertible equipped with the 426 Hemi would be considered nearly inestimable in value and rarity by collectors.

The Challenger R/T ultimately received its moment of lasting stardom when Hollywood cast the car in the all-time hit classic movie “Vanishing Point” released in 1971. In the film, the protagonist, Kowalski, is tasked with delivering a white 1970 Challenger R/T from Denver, Colorado, to San Francisco, California, within an impossibly short timeframe of 15 hours.

Along the high-speed journey, he encounters and interacts with various memorable and sometimes helpful strangers, and finds himself involved in some of the most iconic and thrilling car chases captured on film. Kowalski takes on a larger-than-life persona as a random radio DJ begins covering his cross-country dash, turning him into a folk hero. If you haven’t seen the movie, or if you’ve forgotten most of it since your last viewing, I highly recommend you set aside an afternoon to become reacquainted with this true classic of the automotive film genre.

The Verdict: Boss 429 vs. Hemi Challenger

The battle between the ‘70 Boss 429 Mustang and the ‘70 Challenger R/T Hemi has been fiercely fought, both on the street, on the track, and in the hearts of enthusiasts for decades. Choosing a definitive winner between these two unique and true automotive icons is incredibly difficult. Both represent the pinnacle of the muscle car era’s engineering and excess. However, in this specific clash, there can only be one winner declared, and the nod this month goes to the Dodge Challenger.

The deciding factor, for me and for many, is the legendary 426 Hemi engine. Few would argue against its unparalleled dominance and lasting impact on the automotive industry. It is legendary in the most rugged and formidable sense and seems unlikely to ever be truly duplicated in its historical context and mystique. While the Boss 429 Hp was significant and the car itself a marvel of engineering adaptation, the Hemi holds a slightly higher place in the pantheon of raw, unadulterated muscle car power.

As always, we’d love to hear from you, our readers. Let us know in the comments below which car you prefer and why. Until next time, when we take another ride on a classic highway, stay safe… stay timeless… stay classic!

About the Author

Donny Caccamise is an Automotive Technology Graduate and a Certified Master Technician with more than 40 years of automotive industry experience. Before retiring, he hosted the Nationally Syndicated Automotive Talk Radio Show “Horsepower for an Hour” airing on 161 AM and FM radio stations across the nation. He is a retired member of the ATRA Board of Directors, and retired transmission shop owner. Vintage and classic cars are his specialty. Contact Donny at donnycaccamise@gmail.com