All Aero

The Franklin O-335 (Company designations variations on 6A4) was a series of air-cooled aircraft engines of flat-six configuration.

These engines were commonly vertically mounted and used to power many early helicopters in the United States. They were closely related to the 2A4 and 4A4 2- and 4-cylinder engines. In various subtypes, the 6A4 remained in continuous production from 1945 to the time Franklin’s United States operations ceased in 1975, with versions continuing in Polish production into the 1990s. 6AC ATC 222, 225

In 1947 this engine was modified into a water-cooled version by the Tucker Car Corporation for use in the 1948 Tucker Sedan. Tucker liked the engine so much that he purchased the Aircooled Motors/Franklin Engine Company and it remained under the ownership of the Tucker family until 1961.

Variants:

O-335
Military designation

6A4-124
6 cyl
334ci

6A4-130
6 cyl
334ci

6A4-135
6 cyl
334ci

6A4-140
6 cyl
334ci

6A4-145
6 cyl
334ci

6A4-150
6 cyl
334ci

6A4-165
6 cyl
334ci

6A4-178
6 cyl
334ci

6A4-1854
6 cyl
334ci

6A4-200
6 cyl
334ci

6A4-300
6 cyl
334ci

O-335
6 cyl
334ci

6A-335
180 hp (134.2 kW) at 2,800rpm, 200 hp@3100 rpm
1963-1976

6A-350
205 hp@2800rpm-235 hp@3200 rpm
1965-2002
352.8ci

6AL-335
150 hp (111.9 kW) at 2,600 rpm

6A4-125
125 hp (93.2 kW) at 2,200rpm
1945-1949

6A4-130
130 hp (96.9 kW) at 2,200rpm
1945-1949

6A4-135
135 hp (100.7 kW) at 2,450rpm
1945-1949

6A4-140
140 hp (104.4 kW) at 2,375rpm
1945-1949

6A4-145
145 hp (108.1 kW) at 2,600rpm
1945-1949

6A4-150
150 hp (111.9 kW) at 2,600rpm
1945-1975

6A4-165
165 hp (123.0 kW) at 2,800rpm
1947-1975

6A4-200
200 hp (149.1 kW) at 3,100rpm
1952-1953

6A8-215 / O-500
215hp at 2500rpm
1945-1951
6-cyl
500.7ci

6AC-264 / O-265
110hp at 2600rpm-120hp at 2600 rpm
6-cyl
263.9ci

6AC-298 / O-300
130hp at 2600rpm -155 hp at 2930 rpm
1941-1945
6-cyl

6ACG-264
138 hp at 3100rpm

6AC-425
Military designation O-425

6AG-335
220 hp (164.1 kW) at 3,400rpm

6AC-403 / O-405
200 hp at 2750rpm
1942-1946
6-cyl
403.2ci

6ACG-298-P5
160 hp at 3200rpm
1941-1945

6ACGSA-403
250 hp at 3200rpm
1942-1946

6ACGSA-403
250 hp at 3200rpm
1942-1946

6ACSA-403
220 hp at 2750rpm
1942-1946

6ACT-298
150 hp at 3000rpm
1941-1945

6ACTS-298-K4 / O-300-5

O-300-7
175 hp at 3000 rpm

6ACTS-298
160 hp at 3200rpm
1941-1945

6ACV-245
245 hp at 3275rpm
1944-1958

6ACV-298 / O-300
160 hp at 3250rpm
1944-1946
6-cyl
297.9ci

6ACV-403 / O-405
235 hp at 3275rpm
1942-1946
6-cyl
403.2ci

6ACV-405
Military designation O-405
6-cyl
Vertical fan-cooled helicopter engine

6AG-335
220 hp at 3400rpm
1963-1976

6AG4-185
185 hp (138.0 kW) at 3,100rpm
1947-1950

6AG6-245
240 hp at 3200rpm, 245@3300 (TO)

6AGS-335
260 hp (193.9 kW) at 3,400rpm
1963-1976

6AGS6-245
250 hp at 3200rpm
1944-1948

6AL-315
175hp
6-cyl
1944-1945
ATC 234
315.7ci

6ALG-315
175 hp
1944-1945

6AS-335
240 hp (179.0 kW) at 3,200rpm
1964-1976

6AS-350
235 hp at 2800rpm
1968-1996

6V-335-A
210 hp at 3100rpm
1956-1964

6V-335-A1A
200 hp (149.1 kW) at 3,100rpm
1959-1964

6V-335-A1B
200 hp (149.1 kW) at 3,100rpm
1959-1964

6V-335-B
210 hp (156.6 kW) at 3,100rpm
1956-1964

6V-350
235 hp at 3200rpm
1964-1996
352.8ci

6V4-165
165 hp (123.0 kW)
1947-1950

6V4-178
178 hp (132.7 kW) at 3,000rpm
1946-1960

6V4-200
200 hp (149.1 kW) at 3,100rpm
1946-1970

6V6-245-B16F
245 hp at 3275rpm
1944-1958
6-cyl
425.3ci

6V6-300-D16FT
285 hp at 3275rpm, 300 hp at 3275 rpm + Boost (TO)
1955-1960
6-cyl
425.3ci

6VS-335
225 hp (167.8 kW) at 3,200rpm
1959-1964

Applications:
Aero-Flight Streak-165
Aeronca 15AC Sedan
Bartlett Zephyr
Bartlett LC-13A
Bell 47
Bell HTL
Bell H-13 Sioux
Bellanca Cruisair
Bellanca 14-13
Brantly B-1
Bunyard BAX-3 Sportsman
Cessna 170
Cessna 172
Cessna 175
C.L.A.S.S. BushCaddy L 164
Convair 106 Skycoach
Convair L-13
Culver XPQ-15
Culver XTD3C-1
Doman LZ-1A
Doman LZ-2A Pelican
Fairchild XUC-86B
Fleetwings XBQ-1
Goodyear GA-1 Duck
Goodyear GA-2B Duck
H-23 Raven
Hiller 360
Hiller H-23 Raven
Hiller HTE
Hiller UH-12B
Hirth Acrostar
Jovair 4E Sedan
Kaiser Magic
Kellett XR-8
Maule M-4
Maule M-5-220C Lunar Rocket
McCulloch HUM-1
McCulloch MC-4C
McCulloch YH-30
McKinnie 165
Omega BS-1
Piaggio P.136-L
Procair F.15D Picchio
PZL-Mielic M-20 Mewa
PZL M-26 Iskierka
Republic RC-3 Seabee
Republic RC-1 Thunderbolt
Republic YOA-15
Seibel S-4
SIAI-Marchetti S.205
Sikorsky HO5S
Sikorsky R-7
Sikorsky S-52
Sikorsky XR-6
Sikorsky YH-18
Sikorsky S-52
Socata MS.894 Rallye Minerva
Socata MS 894 Commodore 220
Socata Rallye 220GT
Socata Silvercraft SH-4
Southern Aerocar
Stinson Voyager
Taylorcraft 15
Temco TE-1B
Tucker (automobile)
Temco YT-35 Buckaroo
Van’s RV-8
Waco Minerva 220
Waco Model W Aristocraft
Wagner Sky-Trac 1
Wagner Sky-Trac 3
Wagner Sky-Trac 4 Aerocar
Wittman Big X
Zenith CH-801

Specifications:

6ACV-403
Type: 6-cylinder air-cooled horizontally opposed vertically mounted helicopter piston engine
Bore: 4.625 in (117.5 mm)
Stroke: 4 in (101.6 mm)
Displacement: 403 cu in (6.60 l)
Width: 33.7 in (856.0 mm)
Height: 43.4 in (1,102.4 mm)
Dry weight: 458 lb (207.7 kg)
Valvetrain: OHV, 1x inlet valve, 1x exhaust valve operated by pushrods
Fuel system: 2x Bendix-Stromberg PS-5C pressure updraught carburettors
Fuel type: 80 Octane gasoline
Oil system: 120 S.U. secs (25.1 cs) grade pressure fed at 55 psi (379,212 Pa), dry sump
Cooling system: Air-cooled
Delco-Remy 108567-541 vertical geared electric starter motor
Power output: 245 hp (182.7 kW) at 3,275 rpm for take-off
Specific power: 0.61 hp/in³ (27.758 kW/l)
Compression ratio: 7:1
Specific fuel consumption: 0.5 lb/hp/hr (0.304 kg/kW/hr, 225 US.gal/hp/hr) cruising
Oil consumption: 0.015 lb/hp/hr (0.09 kg/kW/hr, 7 US.gal/hp/hr) cruising
Power-to-weight ratio: 0.357 hp/lb (0.587kW/kg)

6AL-335 / 6A4-150-B3
Type: 6-cylinder air-cooled horizontally opposed direct drive supercharged aircraft piston engine
Bore: 4.5 in (114.3 mm)
Stroke: 3.5 in (88.9 mm)
Displacement: 335 cu in (5.49 l)
Length: 37.4 in (950.0 mm)
Width: 30.8 in (782.3 mm)
Height: 21.6 in (548.6 mm)
Dry weight: 307 lb (139.3 kg)
Valvetrain: OHV, 1x inlet valve, 1x exhaust valve operated by pushrods
Supercharger: mechanically driven supercharger
Fuel system: 1x Marvel-Schebler MA-3SPA updraught carburettor
Fuel type: 80 Octane gasoline
Oil system: 80 S.U. secs (15.6 cs) grade pressure fed at 40 psi (275,790 Pa), wet sump
Cooling system: Air-cooled
Delco-Remy direct cranking electric starter motor
Power output:
(Take-off): 150 hp (111.9 kW) at 2,600 rpm for take-off
(Normal): 150 hp (111.9 kW) at 2,600 rpm at sea level
(Cruising): 112 hp (83.5 kW) at 2,350 rpm at sea level
Specific power: 0.45 hp/in³ (20.35 kW/l)
Compression ratio: 7:1
Specific fuel consumption: 0.51 lb/hp/hr (0.311 kg/kW/hr, 229.5 US.gal/hp/hr) cruising
Oil consumption: 0.01 lb/hp/hr (0.006 kg/kW/hr, 4.5 US.gal/hp/hr) cruising
Power-to-weight ratio: 0.488hp/lb (0.8kW/kg)
B.m.e.p.: 137 psi (945 kPa)