Vintage Motor Trend Road Test: 1964 Plymouth Valiant Signet V8 – Chrysler’s Long-Running LA V8 Has A Valiant Birth

Chrysler’s LA V8, which eventually spawned various displacements as well as V6 and V10 variants, had a long life and became a mainstay of the company after the big B blocks disappeared after 1978.  Chrysler A “poly” 318 was simply too big and heavy to fit in the A-Body compacts, so Chrysler took some weight out of its block through thinner castings and crowned it with better-breathing modern wedge heads that were also lighter and more compact, resulting in the “LA” V8 (Light A). It made its first appearance in the Valiant and Dart in 1964, with 273 cubic inches and a somewhat modest 180 hp.

That was enough to transform the performance of the Valiant; it shaved a full seconds off its 0-60 time versus the 225 slant six. And since it weighed only 35 lbs more than the six and sat back further in the chassis, handling was not affected. The result was a much more dynamic Valiant, especially when teamed with the optional 4-speed manual. The only major negative were the brakes, which should have been upgraded along with the newfound horsepower.

Chrysler had an utterly bewildering array of different V8 engines in the 1950’s and early ’60s, in no less than 25 different displacements and four distinct families (full story here). The A Series V8 first appeared in 1956, and had “poly” (polyspheric) heads, and came in 277, 301, 303, 313, 318 and 326 cubic inch displacements; by far the most common one was the 318. The poly head design was not exactly inspired, and these engines did not breathe as well as the wedge heads popularized by GM. Chrysler soon switched to that superior design on its larger B/RB V8s that appeared in 1958, but the poly 318 lumbered along through 1966.

Apparently Chrysler took a long look at using the poly 318 in the compacts, but wisely decided in the end that it was not going to be a happy combination. So they took the A block and lightened it by using new thin-wall casting techniques and made a few other changes to it. But the big change were the all-new compact wedge heads that crowned it. These and the correspondingly more compact exhaust manifolds allowed the newly dubbed LA (Light A) V8 to fit very tidily in the Valiant and Dart’s engine compartment.

Displacement was reduced to 273 cubic inches, which combined with a mild camshaft and a two-barrel carburetor resulted in 180 (gross) hp. That was a bit less than the 195 hp both Chevy’s and Ford’s smallest V8s made, and that turned out to be a bit of a disadvantage when the 273 was adopted as the base V8 in the larger and heavier B-Bodies, but it certainly made the little Valiant a lot zippier.


The 1963½ Falcon was the first of the Big Three compacts to offer a V8, the 164 hp 260 CID version of the lightweight Windsor V8. In 1964, both Chrysler and Chevy followed suit, with the 180 hp LA in the Valiant and both the 195 and 220 hp versions of the venerable 283 V8 in the Chevy II, which of course had them both beat in terms of performance. And Chevy offered a factory-supplied kit to swap in the more potent 327 V8, all the way to 360 hp. Chrysler wasted little time in perking up the 273 with hotter cam, four barrel carb and a few other goodies for a 235 hp version for 1965.  A vintage review of a ’65 Dart GT equipped with one and the Torqueflite managed a brisker 8.2 second time in the 0-60 compared to the 9.9 seconds of the tested 180 hp Valiant, with the four speed manual. But the TF in the same car would not have been any slower, given its reputation of being as fast as a 4-speed in almost every application (save some all-out SS drag racers who speed-shifted the manual).

Thanks to the 273 V8 weighing little more than the slant six and due to its shorter black, overall weight distribution was barely changed, thus preserving the pleasant handling of the Valiant.

The only downside was that the brakes were not upgraded, and as such were simply not up to the significantly higher performance of the V8 version. But otherwise, the V8 Valiant acquitted itself very well, with a feeling of quality to go along with its lively (if not exactly genuinely fast) performance.

The LA V8 was soon was expanded to 318 size (1966), 340 (1968) and 360, and there was the V10 Viper variant as well as the V6 derivatives. Starting in 1992, they were eventually replaced by the Magnum family, which were a direct development of the LA family, and lasted until 2003.


Related CC reading:

Curbside Classic: 1963½ Ford Falcon Futura V8 – The Economy Compacts Enter The V8 Era

Vintage Motor Trend Road Test: 1962 Chevy II With 340 HP 327 Corvette V8 – Factory Built; Dealer Option Coming Soon!

Vintage Car And Driver Review: 1965 Dodge Dart GT – A Counterpart To The Barracuda

Curbside Classic: 1955 Dodge Coronet – Your Choice of Hemi, Poly or Flat Head