The Best And Worst Years For The Mopar 340 Engine

The series of small-block engines was named “LA”, not because it originated in Los Angeles or Louisiana, but to distinguish it from the old A series that preceded the larger B series. The L stood for ‘low,’ (meaning deck height was less than that of the original A) series and ‘light,’ as the LA engines weighed about 50 pounds more than their siblings. This was due to the thinner cylinder walls of the LA series and updated heads and internals. The first LA engine was the 273, which debuted in the Spring of 1964 under the hood of the 1965 Plymouth Barracuda and its A-body cousin, the Dodge Dart. A 318-cubic-inch version followed in 1967, and a 340-inch version debuted the following year.

While the 273 and 318 were built to be efficient and economical to operate, the 340 was focused on performance. Chrysler advertised it as making 275 horsepower and 340 pound-feet of torque, but Hot Rod Magazine tested a 1968 340 with 320 horsepower and 368 pound-feet. Reducing the advertised numbers would be a good way to help owners reduce insurance costs, a tactic that helped Chrysler sell more cars. When Hot Rod swapped the stock mass for the heads, the output rose to 352.1 horsepower and 395.9 lb-ft of torque.

When they replaced the four-barrel carburetor with a “six-pack” configuration of three two-barrel carbs, the Hot Rod measured 376.1 horsepower at 5,500 rpm and 408.9 lb-ft of torque.