Why NASCAR Banned the Hemi — And How It Came Back

NASCAR banned Chrysler’s 426 Hemi for the 1965 season because it wasn’t available in regular production cars, violating the series’ homologation rules; after Chrysler built and sold “Street Hemi” versions to the public for 1966, NASCAR reinstated the engine. The decision came amid the Hemi’s immediate dominance on track and NASCAR’s insistence that race engines be based on mass-produced, showroom-available powerplants.

What Made the Hemi So Controversial

When Chrysler introduced the 426 cubic-inch Hemi for the 1964 season, its hemispherical combustion chambers, large valves, and superior airflow made an immediate impact. Richard Petty’s runaway victory at the 1964 Daytona 500, along with a Hemi-led sweep of the top spots, highlighted the power gap. NASCAR’s leadership, led by Bill France Sr., was wary of purpose-built “race-only” engines that fans couldn’t buy, and moved to enforce the letter of its production-based rules.

The Rule Behind the Ban

NASCAR’s technical foundation in the 1960s required engines to be “production” units—meaning they had to be available in customer cars in meaningful quantities. The 426 Hemi of 1964 was a race-engine program first, not a street-option. Chrysler had not yet made the Hemi widely available in passenger cars, which put it at odds with the series’ homologation standards.

The 1965 Ban, Explained

For the 1965 season, NASCAR declared the Hemi ineligible because Chrysler had not met the requirement that engines be sold in production vehicles. Rather than quickly retooling its lineup, Chrysler chose to sit out much of the 1965 NASCAR schedule in protest, underscoring how central the Hemi was to its racing strategy.

Key milestones help clarify how the policy unfolded:

• 1964: 426 Hemi debuts; Petty and Chrysler dominate Daytona.
• 1965: NASCAR rules Hemi ineligible for failing production-homologation; Chrysler largely boycotts.
• 1966: Chrysler introduces the “Street Hemi” in Dodge and Plymouth models, meeting homologation; NASCAR reinstates the engine.

Taken together, the timeline shows the ban was regulatory, not punitive: once Chrysler aligned with the production rule, the Hemi returned.

Return and Aftermath

With the 1966 “Street Hemi” offered in showroom cars, NASCAR allowed the engine back. The Hemi resumed its winning ways, but from then on it competed under the same evolving rules as rivals—subject to carburetor sizing, weight, and later aerodynamic constraints designed to keep competition close and speeds in check.

Not Just About Power: The Aero Era and Ongoing Limits

In 1969–1970, Chrysler’s Hemi-powered “aero cars” (Dodge Charger Daytona, Plymouth Superbird) raised separate concerns due to their aerodynamic advantages. NASCAR responded with rules that effectively ended the winged-car era for 1971 by severely limiting engine size or imposing other penalties on such body styles. This was not a renewed “Hemi ban,” but rather a restriction on aero packages that often happened to be paired with Hemis.

Common misunderstandings can blur the specifics:

• The 1965 action targeted homologation compliance, not the Hemi design itself.
• Later NASCAR restrictions focused on aero bodies and parity measures, not a blanket ban on the Hemi.
• Once Chrysler sold Street Hemis to the public, NASCAR allowed the engine back immediately.

These points emphasize that NASCAR’s stance evolved with its core principle: race what you can buy, and keep the field competitive.

Why It Still Matters

The 1965 Hemi ban is a landmark example of how NASCAR has long balanced innovation, spectacle, and accessibility. It reaffirmed the stock-car DNA—competition anchored in production vehicles—while nudging manufacturers to translate racing tech to the showroom. The Hemi’s return in 1966 validated that model and cemented the engine’s legend both on track and on the street.

Summary

NASCAR banned Chrysler’s 426 Hemi for the 1965 season because it wasn’t sold in production cars, violating homologation rules after the engine’s dominant 1964 debut. Chrysler answered by releasing the Street Hemi in 1966, satisfying the requirement and restoring the engine’s eligibility. Later restrictions focused on aerodynamics and parity, not a renewed Hemi-specific ban.

Why was Mopar banned from NASCAR?

Mopar, through its Dodge brand, is not currently in NASCAR because Dodge withdrew from the sport’s top series after the 2012 season. The withdrawal was a result of several factors, including financial difficulties at the parent company Chrysler (partially caused by the 2008 financial crisis), a decline in team interest and competitiveness, and strategic reevaluations by its parent company. However, Dodge is reportedly making a return to NASCAR, with discussions around joining the Truck Series possibly leading to a full Cup Series program by 2027 or 2028. 
Reasons for Dodge’s past departure: 

• Financial Strain: The global financial crisis and Chrysler’s bankruptcy in 2008 heavily impacted the company’s ability to fund its racing endeavors.
• Decreased Competitiveness: A decline in team performance and interest, with other teams moving to different manufacturers, contributed to Dodge’s decision to leave the sport.
• Strategic Reassessment: The withdrawal also reflected a broader strategic decision by Dodge’s parent company to re-evaluate its involvement in motorsports.
• Team Departures: Key partners like Penske Racing left Dodge for Ford after 2012, effectively ending Dodge’s top-level NASCAR efforts.

What is “Mopar”? 

• Mopar is the parts, service, and customer care brand of Fiat Chrysler Automobiles (FCA), which includes Dodge, Ram, and other brands. When people refer to “Mopar not in NASCAR,” they are essentially asking about the lack of Dodge or Chrysler factory involvement in the sport.

Dodge’s rumored return: 

• There are reports and submissions for Dodge to return to NASCAR, potentially starting in the Truck Series and then expanding to the Cup Series.
• The potential return is seen as a positive development for NASCAR, which seeks to increase the number of manufacturers in its series.

What car was banned from NASCAR for being too fast?

That’s exactly what the Dodge Charger Daytona did. The Dodge Charger Daytona was the first car to break 200 mph (321 kph) in a NASCAR race and ended up winning so many races that NASCAR banned it and its sibling, the Plymouth Road Runner Super Bird [source: Davenport].

What was the last year for the Hemi in NASCAR?

1965
NASCAR thus still outlawed the 426 Hemi for use on its tracks in 1965, which found all of the NASCAR Chrysler Hemi corporate sponsor team money moving over to the nation’s drag strips, where even famed NASCAR champs Richard Petty and David Pearson competed in Plymouth and Dodge Hemi drag cars, respectfully, for one …

Was the 440 faster than the 426 Hemi?

No, the 426 Hemi was generally faster than the 440 engine, especially in their stock forms, though a well-tuned 440 Six-Pack could give the 426 Hemi a strong run. The Hemi was a race-oriented engine built for high RPMs and was more powerful in stock form, while the 440 offered better low-end torque and was more practical and affordable for street use. 
Stock Performance Comparison

• 426 Hemi: Opens in new tabKnown for its high-RPM power, the 426 Hemi had a significant power advantage from the factory, dominating on the drag strip and in NASCAR due to its ability to move more air and fuel through its hemispherical cylinder heads. 
• 440 Magnum/Six-Pack: Opens in new tabWhile powerful, the 440 had more weight and a lower torque peak in the RPM range, giving it a better street-friendly feel. In some stock comparisons, the 440’s extra weight could even make it slightly faster than the Hemi in the 1/4 mile, though this was a rare exception. 

Factors Influencing Performance

• Tuning: Modifying a 440, such as with headers, could significantly boost its performance, though the Hemi’s true potential was almost limitless with proper tuning and parts like suitable cams and headers. 
• Purpose: The 426 Hemi was designed as a race engine in “street clothing” and excelled in long-distance racing. The 440 was a more affordable and practical “street brawler” that was easier to maintain and offered more mid-range torque for street driving. 
• Cost & Maintenance: The 426 Hemi was more expensive to purchase and could be challenging to keep running at its peak, whereas the 440 was significantly more affordable and easier to keep in tune. 

In summary, the 426 Hemi was the faster, higher-performance engine, particularly in its element at the racetrack. However, the 440 Six-Pack was a formidable competitor that could often beat the Hemi in shorter, stock form races off the line and on the street due to its lower-end torque.