The Plymouth Valiant was a nice, economical compact car back in 1970. While other Mopar brethren were thumping their chests with big blocks beneath their hoods, Valiant was happy to mind its business and sip lightly on 32-cent-a-gallon fuel. But the folks at Mopar marketing realized the power potential for sticking a bigger engine in the lightweight car to generate high performance numbers. Having seen the racing effect of the 340 and 383 cubic inch Dodge Dart GTS model back in 1969 at drag strips across the land, the move to a 340 ci option for the new Valiant turned Duster product line was a natural.
The Plymouth Duster debuted in late 1969 as a 1970 model featuring sporty lines and a completely redesigned tail end. While the base model was equipped with the slant six, a 318 ci engine was also available as well as a 340 ci engine rated at 275 horsepower. With either a four-speed or automatic transmission, the Duster 340 was a great running car, able to clock 14.7-second runs as reported in several different magazine tests. The 14 x 7-inch Rally wheels, as staple of the performance cars that year, worked well with the performance look of the car but utilized the 4-inch bolt circle also used on the Valiant rather than the larger 4 1/2-inch bolt circle of the bigger Mopars. This unusual bolt circle arrangement resulted in difficultly for many Duster enthusiasts who found it hard to find good custom wheels for these cars.
Inside the Duster was uninspired, a throwback to the original Valiant again with many of the standard early dash components and only a few real gauges to monitor engine condition. Performance models had bucket seats, while the standard version featured a bench with little support. The manual-equipped 340 ci cars incorporated a few extra high performance pieces from the factory including a dual point distributor and 8 3/4-inch ring gear equipped rear end. Automatic transmission-equipped cars did not receive these pieces, to the dismay of many owners who felt they should have been part of any Duster 340 produced at the time.
The Plymouth Duster's extremely low price that made it a hit. The base price with the six-cylinder engine was an amazing $2,172, but for only $400 more, a performance buyer could add the 340 ci engine with four barrel carb, dual exhausts, four-speed manual transmission, a 3.23:1 rear axle, a heavy duty front and rear suspension, front anti-sway bar, front disc brakes, and enhanced instrumentation. For just $2,547, the Plymouth Duster 340 was a real deal and significantly less expensive than the highly regarded $2,900 Plymouth Road Runner and light years away from the Ford Mustang Mach I which tipped the scales at nearly $3,300.
Production Total – Unknown for 340 engine – Presumed to be near 20,000 units for automatic and manual cars.
340 V8 275 bhp @ 5000 rpm, 340 lb-ft @ 3200 rpm.
Transmissions: Three speed automatic (Std.), four-speed manual (Opt.)
Base Price: For Slant Six cylinder Duster - $2,172, Duster 340 - $2,537 nicely equipped.
Car & Driver magazine performance figures:
340/275: 0-60 in 6.2 seconds
1/4 mile in 14.7 seconds @ 94 mph