Chrysler LA Engine - 340 V8

340 V8

As the Detroit power wars heated up in the mid-1960s, Chrysler decided to produce a small block V8 specifically designed for high-performance applications. The goal was to have a lightweight, high output engine equally suited for the drag strip or an oval track. The result of this decision was the 340 cu in V8. Chrysler's engineers increased the 318's cylinder bores to 4.04-inch (103 mm) while keeping the 318's 3.31-inch (84 mm) stroke. Anticipating higher loads resulting from racing operation, the engineers fitted a forged steel crankshaft instead of the cast nodular iron unit used in the 318. A 4-barrel carburetor was mated to a high-rise, dual plane intake manifold. This induction setup fed into a set of cylinder heads that are still considered one of the best of that era. The heads were high-flow items with big ports, and used 2.02-inch (51 mm) intake and 1.60-inch (41 mm) exhaust valves. An aggressive cam was fitted to take advantage of the much better breathing top end. 1968 4-Speed cars got an even hotter cam, but it was discontinued for 1969, where both automatic and manual cars shared the same cam. The engine was equipped with hydraulic lifters and two bolt main bearing caps, leading some to initially underestimate the 340's potential. Power output was officially stated as 275 hp (205 kW) Gross for the 4 barrel and 290 hp (216 kW) Gross for the 6-pack version with triple 2-barrel carburetors. The 340's compression ratio was 10.5:1, placing it near the limit of what was possible on pump gasoline during that era. The 340 also used additional heavy-duty parts, such as a double-roller timing chain, sump-mounted windage tray and a high capacity oil pump.

In 1970, Chrysler offered a special version of the 340 that was specific to Challenger TA and Cuda AAR models. This version featured a heavy duty short block featuring additional webbing in block to allow for 4 bolt main bearing caps (aftermarket installed) and a double roller timing chain. The application-specific cylinder heads featured larger ports compared to a standard 340 and offset rocker arms that allowed the pushrods to be moved away from the intake ports for improved airflow. They featured an aluminum intake manifold with three two barrel Holley carburetors and a dual points ignition system. The best vintage road test data for these cars yielded quarter mile trap speeds of 100 MPH, which suggests roughly 275 "as installed" HP for a car of that curb weight, using Hale's Trap Speed formula (Peak Flywheel HP = (Trap Speed/234)^3 * race weight.

Contrary to undocumented claims regarding engines being "under-rated" during that period, the 340 was one the very few engines to be (almost) honestly rated by SAE Net ("as installed) standards, leading many to claim that the 340 was "under-rated for insurance purposes and really made ." The 275 (Gross HP) rated 340 could actually produce 257 SAE Net HP and could produced 315 HP once all the typical-for-the-era "Gross" HP adding tricks were applied: http://i218.photobucket.com/albums/cc136/harddrivin1le_album/CSERE.jpg By the standards of the day, one could indeed argue that the 340 was "under-rated." Indeed, a multitude of vintage period road tests reveals that a "275 HP" 340 Dodge Dart was fully capable of running toe-to-toe with Chevy's "350 HP" 350 Corvette, which shared a virtually identical curb-weight. Indeed, a "275 HP" 340 Dart was more than capable of holding its own against Chrysler's own "335 HP" 383 big block Dart, which was only 130 pounds heavier. And indeed, a 340 Dart could run with the earlier (1966–1967) street hemi cars, although those cars were substantially heavier (in large part due to the weight of the hemi itself).

Due to the combination of rising gasoline prices, insurance companies' crackdown on high-performance vehicles, and the onset of inflation, the relatively expensive 340 was phased out. It was released in 1968 and remained a high performance engine through 1971. It was severely down-tuned in 1972, with the introduction of low compression (8.5:1), small valve heads, a cast crank, a less aggressive camshaft, and a variety of other unfortunate changes. It was replaced by the 360 engine for the 1974 model year.

• Chrysler Valiant Charger (Australia)
• Dodge Challenger
• Dodge Charger
• Dodge Dart
• Dodge Super Bee
• Plymouth Barracuda
• Plymouth Duster
• Plymouth Road Runner
• Plymouth Sport Fury GT

This engine also powered the French Monica 560.