Inside The Hemi...Six-plus decades on, the 426 Elephant is still a winner
Inside The Hemi
By
Mike McNessor
—
April 28, 2026Six-plus decades on, the 426 Elephant is still a winner
The April 2026 issue (4/26) seemed like a perfect time to look back six decades to 1966 when Chrysler’s 426 Hemi V-8 made a triumphant return to NASCAR.
The Hemi stormed the stock car racing circuit in ’64 then was banned in ’65 due to the elephantine engine not meeting homologation requirements.
The release of the Street Hemi in 1966 gave Richard Petty a blank check to once again run away with The Great American Race—as he and the Hemi had in ’64—making him the first two-time winner.
Also that year, at the behest of Dodge, “Big Daddy” Don Garlits made a brief foray into the Funny Car ranks with an odd-looking 426 Hemi-powered Dart “roadster” driven by Emery Cook. The “Dart II/Swamp Rat IX” became the first Funny Car to run over 200 mph, charging to 200.44 mph, in 8.05 seconds at Sunshine Drag Strip in Saint Petersburg, Florida.
Sure as heck can't do that today. There is no room to get the car stopped before crossing the road at the north end...One more strip gone to eighth mile drags.
Richard Petty’s 426-Hemi-powered Plymouth Belvedere was the first across the finish line at the 1964 Daytona 500, spearheading a one-two-three Hemi finish. All images courtesy of StellantisThe 426 Hemi was indeed a world beater, and an altogether different engine than the first-generation hemi, as it was designed not
to power Chrysler luxury cars but to win races...no homologation? No more stock car racing. Dumasses.
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 426 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 3/8 -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.
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.
The 426 Hemi was designed as a race engine first and a passenger car engine second — unlike the original Chrysler hemi V-8. This is the ’64 NASCAR Hemi.The mechanical camshaft in the 426 race engine was made of cast iron with hardened lobes and rode in five bearings. The ’64 race sticks were aggressive: 0.540 lift, 312 degrees duration and 88 degrees of overlap. For ’66 the ante was upped further: 0.565 lift, 328 degrees duration and 112 degrees of overlap.
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 in 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 seats 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. The pushrods were hollow steel with hardened steel ends.
The drag racing version of the 426 Hemi, topped with two four-barrels.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 race Hemi 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 a 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 competition-style 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’s racing legend only grew after its 1964 race debut and the Street Hemi’s ’66 arrival. 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.
By pairing the new-for-1966 Street Hemi with the new-for-1966 Charger, Dodge homologated the Hemi and created a legend.
Last edited by senor honda; Apr 28, 2026 at 07:09 PM.