At first glance, the 426 HEMI and 426 Max Wedge appear to have a lot in common.
Most obviously, they share the same displacement of 426 cubic inches. This is achieved through an identical bore of 4.25 inches and stroke of 3.75 inches in both engines.
Additionally, both the 426 HEMI and Max Wedge were purpose-built engines designed for high performance racing applications. They represented the pinnacle of Chrysler’s engine development in the 1960s and were feared competitors on the track.
However, once you look beyond the displacement and racing pedigree, significant differences between the HEMI and Max Wedge begin to emerge.
Key Differences Between the 426 HEMI and 426 Max Wedge
Cylinder Head Design
The most fundamental difference between the 426 HEMI and 426 Max Wedge lies in their cylinder head design.
The HEMI, as its name suggests, utilizes a hemispherical combustion chamber. In contrast, the Max Wedge has a wedge-shaped combustion chamber, hence the “Wedge” in its name.
The HEMI head design allows for larger intake and exhaust valves that are angled away from the cylinder walls. This provides superior flow characteristics compared to the Max Wedge heads, where the valves are more shrouded.
Block Differences
To accommodate the unique HEMI heads, Chrysler couldn’t just bolt them to a standard RB engine block. Significant modifications were required, including changes to the block casting to allow the angled valves to fit.
The pistons, valves, valve train, and combustion chambers are all completely different between a HEMI and Max Wedge engine. The HEMI required a dedicated block that shared little with the Max Wedge and other Wedge-based RB engines.
Attachment of Cylinder Heads
Another difference between the two engines is how the cylinder heads attach to the block. On the Max Wedge, the heads are secured using 17 bolts, just like other RB engines.
The 426 HEMI also uses 17 head bolts, but with one key difference. The top 4 bolts are actually studs, with the top 2 studs on each head being longer to accommodate the unique rocker arm shafts.
Racing Success & Dominance
In the early 1960s, the 426 Max Wedge was Mopar’s go-to performance engine. It initially dominated the drag racing scene in 1963, striking fear into competitors.
However, the introduction of the 426 HEMI in 1964 took things to a whole new level and proved to be a nearly unstoppable force in both NASCAR and drag racing. It captured countless wins and cemented Chrysler’s performance reputation. (ref)
While the Max Wedge was a formidable engine in its own right, the 426 HEMI simply outclassed it on the track. The HEMI’s superior breathing and high RPM capabilities made it the ultimate racing engine of its era.
Street HEMI & Later Variants
Although the 426 HEMI was initially built as a pure racing engine, a detuned “Street HEMI” version was introduced in 1966. This allowed the public to experience the legendary HEMI in select production vehicles, albeit in a tamer state.
In the decades since, later HEMI variants have carried on the legacy and mystique of the original 426. Engines like the 6.1L and 6.4L HEMI have powered modern Mopar muscle cars, adding new chapters to the HEMI story.
Even now, over 50 years after its introduction, the 426 HEMI remains a celebrated engine among enthusiasts. Its name is synonymous with tire-smoking performance and the pinnacle of Chrysler engineering.
The Legacy of the 426 HEMI: More Than Just Displacement
While the 426 HEMI and 426 Max Wedge share the same displacement, they are actually quite different engines under the skin. The key distinction lies in the HEMI’s revolutionary cylinder head design, which facilitated its racing dominance.
Although the Max Wedge was a powerful and successful engine in its own right, the 426 HEMI simply operated on another level. It became the stuff of legends on the racetrack and the street.
Five decades after its birth, the 426 HEMI’s place in automotive history remains unassailable. It continues to capture the hearts and minds of gearheads as one of the most iconic and influential engines ever built.
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Nancy Maffia
Nancy received a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.
