Plymouth finally got the performance angle right for 1970, and they went full force into it. The Barracuda was moved over to the E-body platform, which it shared with the new Dodge Challenger. The Barracuda rode on a two inch shorter wheelbase than the similar Dodge Challenger, even though its overall body dimensions were the same. The performance models were called ‘Cudas and featured five different V8s, the 340, 383, 440, 440+6, and the almighty 426 Hemi. The 440s and the Hemi cars received a special high performance suspension to put all that power to the road. Standard Barracudas came with a flat hood, while ‘Cudas came with standard dual non-functional hood scoops. Optional on all ‘Cudas (and standard on Hemi’s) was a very functional shaker scoop, so named because it attached directly to the engine, and poked up through a hole in the hood and thus “shaked” whenever the engine did. The Hemi cost $871 and was installed on just 652 hardtops (out of 17,242) and 14 convertibles (out of 550) copies. It sported hydraulic lifters and was easier to tune than in previous years. The 440+6 was a bargin at just $250 and could keep up with the Hemi till about 70 mph. Both engines were tricky to drive: the 440+6 vacuum-actuated front and rear carbs came on with little warning, while the Hemi’s stiff throttle linkage sometimes snapped all eight barrels open at once.

The Plymouth Barracuda continued into 1971 with minor styling changes, including a segmented grille with twin headlamps, dummy front fender vents, and segmented tail lamps. A full range of engines were available and the top performance models were once again called ‘Cudas. The AAR ‘Cuda was no longer available. To deal with increasingly strict emission laws, Plymouth was forced to detune some of their engines, resulting in a drop in the power ratings. Only 115 Hemi ‘Cudas were sold and Plymouth decided to retire the Hemi engine before it had to be detuned to meet the new emission standards. Therefore, the Hemi would end its reign as the most feared and possibly most influential engine of the muscle car era.

 

Hemi. Few words in the automotive world are more instantly recognizeable than this legendary term. From its original stock car roots to its eventual domination of the world of drag racing, the 426 Hemi has left an indelible stamp on automotive history.

“When we got the green light to go ahead and adapt the hemi head to the big V engine we realized that one day it would be something revered, that it would be something that everyone would look back on as something very special indeed.” — Tom Hoover

Chrysler produced their first engines with hemispherically-shaped combustion chambers in the 1951 [using ideas from other makers as well as their own experience in aircraft engines], but these early motors (301, 331, 354, and 392 cu. in.) share nothing in common with the 426 except for spark plug location and basic valve train arrangement. These “old style” hemis were primarily passenger-car motors, although later versions did power the legendary Chrysler 300 “letter cars” until 1958. Chrysler referred to these engines as the “Red Ram”, “Firedome” and “Firepower” motors throughout their production. Horsepower peaked in 1958 with a 2-4bbl version of the 392 rated at 390 hp. Today, these motors are difficult to find, and those which aren’t in restored vehicles are most often found in fuel dragsters and funny cars, running on alcohol.

 

When the 426 Hemi was introduced in 1964, it was strictly a racing engine. On February 23 of that year, four Hemi-powered Mopars swept the Daytona 500, finishing 1-2-3-4. This single event caught the racing world by surprise and eventually prompted NASCAR to impose stricter production rules on Chrysler. Instead of producing only a few blueprinted Hemi motors each production year, they would instead have to produce several thousand and sell them in “ordinary” production vehicles. Fortunately, Chrysler didn’t throw in the towel on the hemi after this (although they did sit out the 1965 season), and the end result was the slightly detuned street hemi which first appeared in 1966 B-body Dodges and Plymouths.

The hemispherical chamber, as the name implies, is a portion of the sphere. And here you can see the arch shape of the sphere itself. With this we can bring the spark plug into the center of the chamber which is an excellent position for the spark plug. The same shape over in this view allows us to put the valves in a position where when they open, like this inlet valve, it has excellent breathing of the air past the valve seat. This combination of the excellent breathing, of the inlet and the exhaust makes for a very high volumetric efficiency of the engine. … We knew that we could not just put a race engine into production on the street, it just wouldn’t work. But we were able to make a modified version of the engine that became our street Hemi.— Willem Weertman

The street version differed from its racing cousin by virtue of a lower compression ratio (10.25:1), milder valve timing, and different intake and exhaust manifolds. For reliability, cast iron heads were used instead of aluminum. Very little changed inside the 426 Hemi throughout its eight-year production life; only differences in camshaft design (more duration was added in 1968, and a hydraulic bumpstick was used beginning in 1970) really separate the model years. Chrysler never changed the engine’s advertised horsepower and torque ratings, which stood at 425 hp at 5000rpm and 490 foot-pounds of torque at 4000 rpm. Four bolt mains were standard on every 426 Hemi block, street or race.

To list the races which 426 Hemi-powered cars have won would be impossible. Although the motor was basically legislated out of NASCAR in the 1970s, and emissions laws, high production costs, and the insurance industry stopped production of the street version in 1971, the motor still dominates the top drag racing classes more than twenty-five years later. Aluminum versions of the block power virtually all top fuel dragsters and funny cars, and are often used in drag boats and “monster” trucks. Restored Hemi muscle cars carry astronomical prices.
1970 Street Hemi10.28:1 compressionHorsepower (gross)425 @ 5,000Torque490 @ 4,000CarbDual 4-barrel CarterIntake/exhaust duration284° / 284°