From the customers' point of view, power and economy are the most important factors considered in an automobile engine. Other engine features are of lesser importance. Discussion of the Hurricane engine will follow this pattern. A list of technical specifications is at the end of the section.
The Hurricane stands out as one of the most highly developed and perfected four-cylinder engines in the automotive industry. Since its wartime introduction its performance has been steadily improved, vibration cut down, and horsepower increased. Today the Hurricane engine develops 75 horse power and 114 pounds of torque from its 134.2 cubic inch displacement and 6.9-1 compression ratio. This means steady power performance with great economy for the bulk of the jobs to be done by Willys utility vehicles. In those countries where fuel costs are high, the four-cylinder Hurricane gets more miles per gallon of non-premium gas. This spells economy.
This engine can also deliver 33 horsepower from a power take -off point for continuous operation. In the Universal 'Jeep' it can provide a drawbar pull of 2317 pounds. This engine i s designed to do the job and really take punishment.
HURRICANE ENGINE HIGHLIGHTS
The combustion chamber is specifically designed to achieve a fine compromise between high compression and the danger of pre-ignition of fuel.
When compression is too high the fuel ignites on the compression stroke, before the spark plug fires. This results in back pressure that can cause great damage to the piston and rings. On the other hand, too low compression means wasted fuel and power. The Hurricane engine's 6.9-1 compression ratio prevents all of this. See illustration below.
When the engine is used at elevations above 5000 feet and a good grade of gasoline is available, a special 7.4-1 cylinder head is used to offset the drop in atmospheric pressure.
Another feature of the Hurricane cylinder head is the built-in intake manifold. The fuel mixture leaves the carburetor and enters a passage in the cylinder head on its way to the cylinder chambers. Here the fuel mixture is warmed by the adjacent water cooling system passages in the cylinder head. This preheating means more efficient combustion and more power.
The F-head design means the exhaust valves are further away from the intake valves. This construction permits the use of larger exhaust valves resulting in faster, more positive ejection of burned gases. There is no residue to cut power. Since the intake valves are also larger they allow a better flow of fuel air mixture. This results in a more uniform fuel mixture entering the cylinder.
Both intake and exhaust valves are made of chromium steel alloys for greater heat resistance. In addition the exhaust valve guide is chamfered to provide an area for carbon that would normally gather and cause sticking, or improper closing.
A further precaution in this respect is the incorporation of valve rotators on the valve stems. With each stroke the valve is turned slightly resulting in uniform heating and longer valve life. This also wipes off any foreign matter that may have lodged on the valve seat.
By varying the loop spacings in the valve springs, vibrations which cause erratic valve action, are cut down. Wound tightly at top and bottom, and loosely in the center, the valve spring confines vibrations to the middle of each spring and imposes a dampening effect from both ends on even these slight disturbances.