Pratt & Whitney R-4360 Wasp Major


The R-4360 engine was used to power various post-WW-ll USAF bombers, cargo-transport, and aerial tankers, including B-50, KB-50, B-36, C-97, KC-97, C-119, and C-124 aircraft. It represents the most technically advanced and complex reciprocating aircraft engine produced in large numbers in the United States. The passing of the KC-97 and C-97 series aircraft from Air Force inventory in the late 1970s marked the closing of the era of both the large piston and turbo-supercharger within the USAF



4360 engine running on the test stand. The exhaust collectors have been removed.


Pratt & Whitney R-4360 Wasp Major
Model:R-4360 CB2
Type: 28 cylinders, 4 row radial, air cooled, geared drive, turbo-supercharged, 4 cycle. T.C.247.
Construction: 5-piece forged aluminum alloy crankcase. Cylinders with steel barrels and shrunk on forged aluminum alloy cooling muffs, and forged aluminum alloy heads. Cylinders arranged helically around crankcase to facilitate cooling. 1 inlet valve and 1 exhaust valve (Inconel "M") per cylinder actuated by push rods. 4-throw 1-piece counterbalanced crankshaft supported in 5 plain bearings. Planetary spur reduction gear, ratio 0.375:1. Single propeller shaft, with provisions for Hydromatic propeller. Torque-meter.Hydro-Aire control actuators.
Supercharger:Gear-driven 1-speed supercharger, ratio 6.374:1. Provision for General Electric CH9 1-sage turbo-supercharger. Aftercooler.
Fuel system:1 Bendix-Stromberg PR-100B3 4-barrel downdraft injection type carburetor with mixture control. Optional equipment: 1 Chandler Evans 100CPB9 downdraft injection type carburetor. Provision for water injection, with Bendix Products K2 or M1 water regulator.
Ignition:4 Bendix-Scintilla S14RN-15 low-tension dual magnetos. 2 18-mm long reach spark plugs, with 1 high-tension booster coil per spark plug, per cylinder. Shielded ignition system.
Lubrication:Pressure feed, 80-85lb./sq. in. (5,6-6,0 kg.cm²). Dry sump.
Starter:Optional. Eclipse 36E07-2 electric starter can be used.







Bore:5.75 in.146 mm
Stroke:6.00152 mm
Displacement:4.363 cu.in.71.5 lit
Compression ratio:6.7:16.7:1
Length: (engine only)96.5 in.2 451 mm
Diameter:55.01 397 mm
Frontal area:16.5 sq.ft.1.35 m²
Weight: (engine only)3,670 lb.1 665 kg
Weight/Horsepower:1.05 lb./h.p.0.48 kg/hp
Fuel Consumption: (cr.)0.43 lb./h.p./hr.195 g/hp/hr
Oil consumption: (cr.)0.015 lb.h.p./hr.11 g/hp/hr
Gasoline Grade:115/145 grade115/145
Oil Viscosity:100 S.U. secs.20.5 cs
Output/Displacement:0.80 h.p./cu.in.49.0 hp/lit
Output/Piston Area:4.81 h.p./sq.in.0.75 hp/cm²
Piston Speed: (max)2,700 ft./min.13.t m/sec.
B.m.e.p.: (max)235 lb./sq.in.16.5 kg/cm²
Rating: (take off, wet)..3.500 h.p./2,700 r.p.m./60.o in. (1 524 mm)+15.0 lb.
Rating: (take off dry)...3250 h.p./2,700 r.p.m./60.0 in. (1 524 mm)+15.0 lb.
Rating: (normal)...2,650 h.p./2,550 r.p.m. /5,500 ft. (1 680m)
Rating: (max. cruising)...2,800 h.p./2550 r.p.m./3,500 ft. (1 070 m)



The above ratings are at 500 ft. (150 m) and 700 ft. (200 m), respectively.





R-4360 ready to be installed.




R-4360-20: Military engine similar to R-4360-CB2, but without water injection. Same dry ratings.


R-4360-53: Military engine similar to R-4360-CB2, but with direct fuel injection and other modifications. 3,800 h.p./2,800 r.p.m./take-off, wet. 115/145 grade gasoline.


R-4360-59,-63: Military engines similar to R-4360-53


Note: Ford Motor Co., Engine Division manufactured the R-4360-53,-59,-63 engines.

Cylinders... The cylinders which are similar to those of the R-2800 Series, are arranged helically around the crankcase and pressure baffles are provided for individual cylinders and for each bank of four. All cylinders are completely interchangeable.


Pistons... Generally the same as for the Double Wasp, with reinforced internal bosses.


Connecting Rods...Rod assembly for each row of seven cylinders consist of master rod with detachable cap, two piece lead silver bearing, and six I-section articulated or link rods. Each link rod has a bronze bushing at the piston end and rides on a silvered knuckled pin.


Crankshaft... One piece crankshaft of forged steel has four throws and is supported in the crankcase by five steel-backed lead-silver main bearings. Weights of the reciprocating parts connected to the crankpin are counterbalanced by two fixed and two bifilar counterweights.


Airscrew Shaft...Supported at the crankshaft end by a plain lead-bronze bearing and at the air-screw end by a roller-bearing to carry radial loads and a deep-groove ball-bearing witch absorbs engine thrust.


Crankcase...The power section case made up of five sections, all except the front and rear sections being substantially alike. The parts for the power section are machined from aluminum forgings and are held together with through bolts. All other crankcase sections are magnesium castings. Attached to front of power section by studs is the magneto section, whichmounts four interchangeable magnetos and contains the torquemeter. The nose section houses the planetary reduction gearing and has provision for full-feathering, reversible airscrew governor. Attached to rear of power section by studs in the supercharger housing, enclosing the supercharger drives and impeller. Behind the supercharger housing, also attached with studs, is the accessory section. On this is mounted a down-draft pressure type carburator. This section houses the accessory-drive mechanism and provides mounting pads for the radial mounting of all accessories and automatic power controls to permit greater accessibility for servicing. Normally nothing is mounted to the rear of the engine but co-axial accessory drive maybe provided as optional equipment.


Valve gear...Rocker boxes are part of the cylinder head, extending four and aft. Rocker arms with plain bearings are actuated by enclosed push-rods. Double-track self-mounted cams inside the crankcase between the rows of cylinders operate the exhaust valves of the forward row of cylinders and the intake valves of the aft row. Cams are driven by reduction-gears from the crankshaft at one-sixth crankshaft speed.


Induction System...Stromberg four-barreled pressure-type carburetor, with automatic mixture control, idle cut-off, primer tubing and distributor. Metered fuel is carried through internal passages and is thrown centrifugally through small holes between the impeller blades to mix with the combustion air. The fuel-air mixture, after passing through the diffuser to the blower rim, is carried to the cylinders through seven intake pipes, one for each bank of four cylinders.


Supercharger...There are two basic types in unrestricted engines: a single-stage single-speed supercharger suitable for use with an exhaust driven turbo-supercharger, and a single-stage hydraulically-driven variable-speed supercharger. The two-piece impeller assembly consists of a machined impeller the straight blades of which are blended with the curved entrance blades of an inducer.


Ignition System...Four Scintilla magnetos, each with an internal distributor, operate at one-half crankshaft speed. Dual ignition.


Lubrication...Forced feed lubrication provided by a gear-type oil pump to all parts of the engine.


Reduction Gear...The planetary reduction gears are of Pratt & Whitney design and are spur gears with ratio of .375:1.


Accessory Drives...All accessories mounted radially on the periphery of the rear section. All accessory drive-gears driven by a bevel-gear revolving at crankshaft speed.




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