This will mark the first time an eight-cylinder power plant has been available for the popular Dart.
"This engine was specifically designed for those customers who wish to combine the increased performance of a V-8 with the maneuverability of a compact car," Dodge General Manager Byron J. Nichols explained.
"To be known as the Charger 273, this engine will be the smallest and lightest V-8 built by Dodge but will offer a performance potential equal to that of the 318-cubic-inch engine now provided in standard-size Dodge V-8 models." [Editor's note: The 318 described here is NOT the same as the 318-cubic-inch engine later available in the Dodge Dart.]
The horsepower rating -- 180 hp at 4,200 rpm -- means that the 273 will move the Dart from zero to 60 miles per hour in one-fifth less time than will the optional 225-cubic-inch Slant Six engine, Dodge Chief Engineer George Gibson reported.
The torque output of 260 lbs.-ft. at 1,600 rpm is the result of studied efforts by engineers to match the 273 to the Dart power train components.
In effect, the lively performance qualities which have always been characteristic of the Dart can now be extended to an even greater range.
Of these goals -- all of which were ultimately achieved -- two were of special importance.
First, the overall dimensions had to be such that the new engine would fit in the Dart engine compartment -- and provide good access for service.
Second, the engine had to be light enough so that it would have no adverse effect upon the excellent ride and handling characteristics of the Dart.
Solutions to both problems were practicable.
The engine profile was lowered by means of a flat, single plane intake manifold design and a reduction in the height of the air cleaner.
Design changes were accompanied by a unique left exhaust manifold and a shallow pocket formed in the left side of the block, both tailored to provide extra clearance for the Dart steering gear.
| Type | 90-degree, V-8 |
| Bore | 3.625 inches |
| Stroke | 3.312 inches |
| Displacement | 273.5 cubic inches |
| Horsepower | 180 at 4,200 rpm |
| Torque | 260 lb-ft. at 1,600 rpm |
| Valve Arrangement | In-line, overhead valves |
| Compression Ratio | 8.8 to 1 |
| Fuel Grade | Regular |
Sand cores for the 273, however, are cured in heated core boxes and as a result they are hard when removed and can be used immediately. Because the 273 cores are produced with such precision through this method, they can be fitted together with very close tolerances. The wall thickness of the casting is carefully controlled and unnecessary weight is eliminated.
Other factors contribute to the accuracy of the castings. Fewer cores are needed, and these are fastened securely into place by interlocking core prints. This reduces the tendency for the cores to shift in the molds as they are being handled and as the metal is being poured.
A direct effect of this careful fitting and mating of the 273 cores is noticeable in later stages, when it is not necessary to remove so much surplus metal to reach the finished dimensions.
The short 3.31-inch stroke is combined with a smaller bore size of 3.625 inches to arrive at the 273.5-cubic-inch displacement goal, an ideal size for a car of the Dart wheelbase.
Twelve cores are required to cast the 273 blocks. By using a special tappet chamber core, the foundry is able to eliminate much unnecessary metal from the complex casting area at the top of the block.
The 25-inch-long crankshaft is of forged steel for extra durability. Main journals are 2.5 inches in diameter, supported by five babbitt-on-steel main bearings, and rod journals are 2.125 inches in diameter. Crankshaft journal overlap is .66 inches. Thrust is taken on the Number 3 bearing.
The short connecting rods are designed on 6.123-inch centers and forged to a tapered I-beam section that combines maximum strength with minimum weight.
Rods are conventional, with bushings at the ends into which the piston pins are fitted. The pins are full floating and retained in the piston by spring steel lock rings. Piston pin bores are offset by .06 inches from the piston centerlines to prevent piston slap.
Two compression rings, .78 inches wide, are used with each piston. The oil ring is three-piece with two chrome-plated steel rails separated by an expanding spacer. The total ring lineup provides excellent oil control.
The cam-ground, aluminum alloy pistons have flat heads, slightly notched in four places to allow extra valve and head clearance, and to facilitate their use in either bank. Two steel inserts are cast into each piston skirt so that it expands at the same rate as the cylinder bore when the engine temperature increases.
Combustion chambers are designed to obtain an 8.8 to 1 compression ratio with flat head pistons. The shape of the chambers is a modified wedge with the spark plugs situated as near to the center of volume as possible for equal flame travel and uniform combustion.
Overhead valves are set at an 18-degree angle from the bore axis and operated by the camshaft through a system of mechanical tappets, tubular push rods, and pearlitic malleable iron rocker arms of a new design.
The valve layout is such that intake and exhaust valves are situated in a straight line along the cylinder head, which simplifies the rocker arm and shaft arrangement. Valves are tulip-shaped for effective seating, and have rubber cup seals to shield both intake and exhaust valve stems from excessive oil splash. The intake valve has a head diameter of 1.78 inches and the exhaust of 1.50 inches.
As the valves are in-line, both intake and exhaust rocker arms are the same. Adjustments are made by a screw in the push rod end. The rocker shaft seats in half-round notches that are broached in the top of each support bracket and fastened down by stamped retainers and screws. These brackets, together with the valve guides, are cast integrally with the heads.
Push rods are tubular steel shafts, .315 inches in diameter, with hardened steel inserts on each end. They are actuated by mechanical tappets. The 273 camshaft is 22.04 inches long and made of a chromium molybdenum-alloyed cast iron.
Each head is effectively sealed to the block by a composition steel-reinforced and rubber asbestos gasket, and fastened with 10 head bolts spaced symmetrically along each side. Head covers have a new type of cork gasket and are attached at the flanges by five screws.
The new single plane manifold design gives the desired flat, low profile.
The exhaust manifold on the right side is a three-branch, low runner design with a center outlet; however, on the left side the manifold has a high runner that extends to the rear of the engine before descending in an S-shape to clear the steering gear. Despite the different configurations, the efficiency of both is relatively equal.
Adequate clearance is provided to the spark plugs on each bank. The plugs are protected from exhaust manifold heat by steel shields that are integral with the exhaust manifold gasket.
Both right and left hand exhaust manifolds have ball-joint seating connections at the exhaust pipe flanges for each alignment.
The air cleaner used is the paper element type, and a cable-operated throttle linkage serves to dampen the transmission of power plant vibration and movement.
Matching holes at the rear of the block and cylinder heads allow the coolant to travel upward from the block to the heads. From the heads, the coolant passes through the thermostat housing at the front of the intake manifold and on into the radiator top tank.
Uniform metal temperatures are maintained throughout the engine by this type of series flow pattern. Coolant capacity is 17 quarts.
Passages drilled from this gallery supply oil to the main bearings and camshaft bearings. Additional passages feed the left gallery to lubricate that tappet bank.
The rocker shaft and valve rocker arms are lubricated by holes drilled in the cylinder head and block that intersect the Numbers 2 and 4 camshaft journals.