With little fanfare, Chrysler’s trusty L-head six faithfully served millions of Plymouth and Dodge owners from 1933 to 1959.
When we reflect on the engines in Chrysler history, we naturally tend to think of the original Hemi V8, or the mighty V8s of the muscle era: Max Wedge, 440 Magnum V8, Six Pack and Six Barrel, 426 Hemi. But for decades, the most popular engine in Dodge and Plymouth cars was a modest L-head inline six that, for its first 10 years in production, was rated at less than 100 horsepower. Introduced back in 1933, it remained in service all the way through 1959, powering millions of cars. It’s well past time for a closer look.
When the Plymouth/Dodge six was introduced in 1933, the Chrysler Corporation was well into in the process of modernizing and consolidating its many engine lines, some inherited from Maxwell and Dodge Brothers. A totally conventional L-head, inline design, the engine was intended from the start to serve both Plymouth and Dodge. At first, the two were differentiated by giving the Dodge a larger displacement: 189.8 cubic inches for Plymouth (3.125-in bore, 4.125-in stroke) and 201.3 CID for Dodge (4.375-in stroke). Through the years the displacement was progressively increased, and starting in 1954 the displacement for Dodge and Plymouth was standardized at 230.2 cubic inches.
Inline sixes were ubiquitous throughout the Chrysler Corporation’s brands in the ’30s and ’40s, and they were mostly similar with four main-bearing layouts. The Plymouth/Dodge six was distinguished by its short-skirted cylinder block design, in which the crankcase extended down only .125 inches from the crankcase centerline to reduce weight and cost, while Chrysler’s other sixes typically used a deeper skirt. One feature shared by all these Chrysler sixes was their staggered bore centers. In this instance the numbers 2/3 and 4/5 cylinders were spaced .250 farther apart in the block to accommodate the center two main bearings.
Cast into the iron block were six individual intake ports and six exhaust ports conjoined into three outlets. Intake and exhaust valves of the L-head layout were parallel to the cylinder bores, with 1.43-in diameters for both. In 1942, the intake valves were opened up to 1.53-in, where things remained through 1959. The camshaft was designed for solid, mushroom-type lobe followers with a wide foot. Throughout its life, the engine was never upgraded to hydraulic valve lifters.
Shown above is the final 1959 top end and cylinder head. But in fact, while the external hardware and accessories evolved through the years, the internal design remained essentially unchanged. In its initial 1933 form with a 5.5:1 compression ratio, the Plymouth six was rated at 70 hp at 3,600 rpm and 130 lb-ft of torque at 1,200 rpm. The final Plymouth version of the flathead six, with 230 cubic inches and an 8:1 compression ratio, developed 132 hp at the same 3,600 rpm. Back in 1933, the Chrysler engineers probably never imagined their engine would remain in production for 26 years. But all things must pass, and for 1960 the flathead was finally retired to make way for Chrysler’s all-new Slant 6, and you can read about it here.
Note: Much of the information here was obtained or confirmed in Chrysler Engines 1922-1998 by Willem L. Weertman, 2007, published by SAE International. The book, available in hardcover at Amazon or in digital form at SAE.org, is indispensable to anyone with a serious interest in Chrysler engine history.
If I recall correctly these were used in the original military style Power Wagon until its production ended in 1969 along with being sold as a stationary power plant.
Yes, sir. 230 CID. Rock solid engine, not terribly powerful but rugged and simple.
FWIU the original Power Wagon was in production until well into the ’70s but export only after ’69 since by that point the main buyers were oil exploration in the Middle East and NATO-aligned foreign militaries wanting a cheap, proven army truck.
Allpar has some good history on the original power wagon:
https://www.allpar.com/d3/model/ram/powerwagon.html
Quiet smooth reliable boring. My first car: 1954 Plymouth ewwwww.
Mine was an ’81 Omni Miser. Oatmeal Mopars unite!
My second car, in the mid-1970s, was a 1947 Dodge pick-up. Effective both as novel looking transport and also speeding ticket repellent. Despite being well used-up and replete with worn piston rings, I cannot recall a circumstance, including deep-freezes where it refused to start and run.
Another Jim Zeder masterpiece, all years interchange direct bolt-in (except early ’33-’34 bellhousings). Unmatched production, commercial, agriculture, military, war and motorsports record.
Outrun any Chevy stovebolt, most Fords and Hudson needed dual carbs to keep up…
That ole L-head engine was reliable, owned 2 a 1956 Dodge P/u & 1957 Dodge HT.
Unless mentioned, it should be noted the Chrysler flathead 6 was used in a host of industrial applications. From forklifts to portable welders to search lights, transfer pumps and everything in-between. It was the standard powerplant for military and civilian use well into the 70s. While the Slanty was novel, it too had a lot of applications in vehicles, but can’t hold a candle to the flattie.
You can see how the L-head six became the universal choice in the U.S. auto industry in the ’30s. Far smoother than a four, and try to imagine a six-cylinder engine with a lower component count.
My 55 plymouth 6 took me through high school and college. Yup, smooth and reliable. Now I have a 55 plymouth V8. Big powerful difference. Hardly anything to maintain.