It’s been 60 years since Chrysler’s all-new 426 Hemi V-8 dominated the 1964 Daytona 500 and took its first step to becoming of the great American high-performance icons. Three ’64 Plymouths, led by Richard Petty’s #43 Belvedere, grabbed the top finishing spots on February 23 of that year, while Jim Paschal’s Hemi powered Dodge Polara came in fifth and Junior Johnson’s Dodge nailed down 10th. Hemi cars shattered records and dominated qualifiers leading up to the 500, then went on to score more than two-dozen victories for ’64 — as well as earning Petty a NASCAR title.
For ’65, NASCAR banned the Hemi, citing the lack of production engines for hom*ologation but, with the arrival of the Street Hemi, the elephant charged back into NASCAR competition for ’66, picking up victories where it left off.
Meanwhile, on the quarter-mile tracks of America, Hemi-powered Super Stock and Experimental class racers thundered through the ’64 season setting the stage for decades of drag race wins to follow. In Top Fuel, the 392 was a dominant force when the 426 arrived, but that changed forever, in 1966, when “Big Daddy” Don Garlits made a 7.40-second, 219-plus-mph pass in a 426-powered dragster.
The 426 Hemi was an altogether different engine than the first-generation hemi. But the 1951-’58-vintage V-8 Chrysler/Imperial/DeSoto/Dodge V-8s put Detroit on notice and showed the world the hemispherical combustion chamber design’s performance potential.
The 426 had an edge over the original hemi, as it wasn’t designed as a luxury-car engine. It was built to win races — specifically stock car races.
Development began in January ’63 and the plan was to win the ’64 Daytona 500 — but that almost didn’t happen. During full-throttle engine testing in late January ’64, the right side cylinder bores in Hemi test mules began cracking. So, in early February, new blocks were cast with thicker bore walls and then carefully stress relieved by reheating them to 1,200 degrees and allowing them to cool slowly. How close was it? The engine block in Richard Petty’s car was cast on February 10 and won the 500 less than two weeks later.
Inside the Engine Block of the 1964 Daytona 500-Winning 426 Hemi
The 426 Hemi block was based around the RB wedge block and is basically the same size — but it’s unique to the Hemi. The block was cast out of tin-alloyed iron and had 3-inch-deep skirts. Through those skirts, main caps two, three and four were cross-bolted using ⅜-inch bolts. The block also had bosses cast into the lifter valley to accept head studs that were fastened by a nut located in the valley. This unique arrangement was necessary in order to prevent the topmost inner head bolt from interfering with the intake port. (The 426 used five bolts per cylinder for maximum clamping force, but retained the proven valve angle and layout of the first-generation hemi which used four bolts per cylinder). The Hemi block also had four oil drain-back holes, one in each corner, that aligned with oil holes in the heads.
A Look at 426 Hemi Pistons, Rods and Crankshaft
Pistons in the 426 were impact-extruded aluminum with high domes and valve reliefs in order to produce a 12.5:1 compression ratio. The connecting rods were made of forged steel and set up with floating pins. Initially, the rod caps were fastened with 7/16-inch bolts, but instances of spun bearings, when Hemis revved over 7,000 rpm during later testing, led to the use of ½-inch bolts by 1966.
The 426 Hemi’s crankshaft was forged steel with 2.75-inch main journals and 2.375-inch rod journals. It was heat treated, then machined, then shot peened and finally the journals were finish ground. The crank was then nitride hardened and hand lapped with care taken not to lap through the hardened layer. What Camshaft Did the 426 Race Hemi Use?
The mechanical camshaft in the 426 race engine was made of cast iron with hardened lobes and it rode in five bearings. The ’64 race sticks were aggressive: .54 lift, 312 degrees duration and 88 degrees of overlap. For ’66 the ante was upped further: .565 lift, 328 degrees duration and 112 degrees of overlap.
Stellantis
The 426 Hemi’s "Hemispherical" or Domed Heads
Of course, the Hemi’s heads were its not-so-secret weapon. The original race heads were made of cast iron (aluminum race heads would arrive for 1965) and the volume of the domed combustion chambers was a cavernous 172.7 ccs. The 2.25-inch intake valves and 1.94-inch exhaust valves were positioned across from each other with an “included angle” of 58.5 degrees between the intake and exhaust: the intake valve was angled 35 degrees from vertical while the exhaust was angled 23 degrees from vertical — eliminating valve shrouding. To make use of the fast and free-flowing intake charge, the spark plug was placed as close to the center of the combustion chamber as possible — this cut back on the distance that the ignition fire needed to travel. Water jackets were incorporated around the exhaust valves and valve guides, while partial water jackets cooled the spark plug seat and the intake valve seat. Forged steel rocker arms (eight per side) rode on steel tube rocker shafts (two per side – one for the exhaust and one for the intake) that were attached to the head with five cylinder head bolts each. The pushrods were hollow steel with hardened steel ends.
The 426 Hemi’s Intake, Carburetor and Exhaust Headers
The ’64 competition NASCAR engine used a conventional aluminum intake fed by a single Holley four barrel. The intake was a dual-plane style with top and bottom runners but there were slots cut between the runners connecting them to ensure maximum flow at high rpm.
(The ’66-vintage used the more distinctive and free flowing “bathtub” or “plenum ram” design intake) The carburetor was an 850-cfm with 1 11/16 x 1 11/16 in. throttle bores and “Le Mans-style” fuel bowls
The NASCAR engines inhaled through a 23.5-inch “cowl-induction” air cleaner with rectangular opening in the rear that connected to the car’s heater plenum and drew air through slots in the cowl at the base of the windshield.
All of that spent air and fuel exited through headers made of 2-inch steel tubing welded into cast adapters that bolted to the exhaust ports and were tied together in massive 4-inch collectors.
The 426 Hemi is Still a Winner
The 426 Hemi’s racing legend only grew after its 1964 debut and the basic design has soldiered on influencing today’s 10,000-horsepower Top Fuel and Funny Car engines. Meanwhile Dodge and Plymouth 426 Street Hemi muscle cars are still among the hottest collectibles in the market — all due to the engine’s take-no-prisoners approach to winning on Sunday.
This is the drag racing version of the 426 Hemi, topped with two four barrels. Each carb feeds a cylinder bank on the opposite side. (Right carb, left bank)Stellantis