Jeep Legend - Hurricane



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.



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.

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.


The lightweight, precision ground, aluminum alloy pistons weigh about half as much as a cast iron counterpart. This means less vibration, faster acceleration, and greater engine speeds. Each piston is tin plated to reduce wear and scuffing during the break-in period and under cold starting conditions.

"T"-slots are cut into each piston so that heat expansion takes place in the slot rather than on the piston's outside surfaces which contact the cylinder walls. Piston and cylinder wear is noticeably reduced in this way. Also from this feature it is possible to fit pistons in the cylinders to very close tolerances thereby eliminating piston slap (knock).


The connecting rods are drop-forged steel of the "I" beam style - the strongest possible construction for the weight involved. Since the 9-3/16" Hurricane connecting rods are longer than conventional rods, their angle to the cylinder wall is decreased. This means less pressure of the piston against the cylinder wall which in turn decreases cylinder wear.

The rods are balanced in sets of four. Balance varies no more than 118 ounce, reducing vibration to a minimum.

An oil hole through the bearing end of the connecting rod carries oil from an outlet in the crankshaft and sprays it against the cylinder walls. This gives direct lubrication to the pistons and rings.

The bearings used in the connecting rods are precision-made, steel-backed, babbitt bearings and are easily replaced without using shims. The thin wall of the bearing conducts heat quickly to the rod itself, giving longer life to the bearings.


The crankshaft, like the connecting rods, is drop-forged for greater toughness and strength. There are three main bearings -- all precision made, babbitt-faced steel shells that are easily replaceable. The crankshaft is balanced first as a single unit - then balanced again after the fly-wheel and clutch have been attached. Minimum vibration and less engine wear at any speed is thereby assured.

The rear main bearing is provided with a Neoprene seal that keeps the oil in. This is especially important when the vehicle is climbing steep grades. Oil is prevented from passing out into the flywheel and clutch housing.


The camshaft is alloy cast iron and is mounted in four bearings. It is driven by a helical-cut gear on the crank-shaft, which engages a helical cut fiber gear on the camshaft. The helical-cut provides a sliding engagement of the gear teeth, assuring quiet operation. The fiber material also contributes to quietness, yet gives positive valve action.

The contour of the cams assures a quick and high lift to the valves resulting in quiet operation.


The flywheel of the Willys engine is light in weight. This adds to acceleration, an important feature in a versatile vehicle. The flywheel is accurately balanced as a unit to reduce vibration. The face of the flywheel acts as the driving member for the clutch disc. On the outer edge of the flywheel is a hardened steel gear, which is engaged by the starter. During manufacture, this gear is heated, then placed on the flywheel where, in cooling, it shrinks to a tight permanent fit.


The Hurricane has a forced-feed lubrication system. Oil is carried under pressure to the main bearings, connecting rods, and camshaft bearings.  Timing gears are lubricated by a jet of oil at the front of the timing gear case. As mentioned previously, the cylinder walls, pistons, and pins are lubricated by a stream of oil through a hole in the connecting rod.

The oil intake is the floating type that permits only clean oil to enter the system. Dirt, water and other abrasives remain on the bottom of the crankcase below the intake level.



This completes the picture of the Hurricane engine. Most of those features that have definite benefits to the user have been emphasized. The specification table at the end of this section includes detailed information on the fuel system, electrical system, cooling system and lubricating system, as well as complete engine specifications.

01  Fan

27  Cylinder Block

02  Water Pump

28  Tappet Adjusting Screw

03  Water By-pass Hose

29  Rear Engine Plate

04  Thermostat

30  Camshaft

05  Water Outlet

31  Flywheel

06  Piston

32  Rear Bearing Cap Packing

07  Rocker Shaft B racket

33  Rear Crankshaft Packing

08  Rocker Arm Shaft

34  Inlet Valve Tappet

09  Rocker Arm Shaft Spring

35  Crankshaft

10  Breather Cap

36  Bearing Dowel

11  Rocker Shaft Lock Screw

37  Oil Float Support

12  Exhaust Valve

38  Oil Float

13  Inlet Valve

39  Oil Pan

14  Inlet Valve Spring

40  Connecting Rod

15  Inlet Valve Guide

41  Front Engine Plate

16  Rocker Arm

42  Crankshaft Gear

17  Exhaust Valve Adjusting Screw

43  Crankshaft Oil Seal

18  Rocker Arm Cover

44  Crankshaft Pulley

19  Ignition Cable Clip

45  Crankshaft Gear Spacer

20  Vacuum Tube

46  Timing Gear Oil Jet

21  Cylinder Head

47  Camshaft Gear Bolt

22  Inlet Valve Push Rod

48  Camshaft Gear Spacer

23  Exhaust Valve Guide

49  Camshaft Thrust Plate

24  Exhaust Manifold

50  Camshaft Gear

25  Exhaust Valve Spring

51  Fan Belt

26  Piston Pin