Atomic Four Specifications
Written by Robert Hess
Atomic Four Engine Service
Vancouver, Canada
Universal
Atomic Four: UJ, UJR, UJVD
Universal Atomic Four Stevedore: UJS, UJSR, UJSVD
Specifications & Dimensions | Models | 5101
/ UJ - base configuration Atomic Four 5111 / UJS - Stevedore configuration for Canadian market, power limited to 15 hp with intake manifold restriction) 5102 / UJR - reduction gearbox mounted on transmission, 2.04 ratio standard 5112 / UJSR - Stevedore configuration with reduction gearbox mounted on transmission, 2.04 ratio standard 5103 / UJVD - 20° angle Walter V drive gearbox mounted on transmission, 4 gear ratio options including 1:1 5113 / UJSVD - Stevedore configuration with 20° angle Walter V drive gearbox mounted on transmission, 4 gear ratio options including 1:1 |
Type | Vertical, in line, 4 cycle, L (flat) head | |
Serial Number Locations | Pre
1969: stamped on right, forward side of block above
starter motor Post 1968: stamped on block above flywheel housing, and on an id tag glued to top of manifold Post 1977: stamped on block above flywheel housing, on an id tag glued to top of manifold, and on an id tag glued to front of the flywheel housing cover |
|
Cylinders | 4 | |
Bore | 2.562 in | |
Stroke | 3.125 in | |
Engine displacement (swept volume) | 64.44 cu in / 1055.98 cc | |
Compression Ratio | 6.3:1 | |
Cylinder Block | Cast en-block with marine chrome nickel alloy iron crankcase & full length water jackets | |
Cylinder Head | Marine chrome nickel iron detachable head | |
Crankshaft | 2 main bearing, high carbon steel, fully counterweighted, statically and dynamically balanced, uses insert bearings | |
Connecting Rods | Drop forged, high carbon steel, floating piston pin, insert bearings | |
Pistons | Cast aluminum, flat-top, 3 ring - 2 compression rings and 1 oil control ring, floating piston pin retained by steel circlips, pin offset .005", expansion slot on non-thrust skirt | |
Oil pan | Marine chrome nickel iron, one piece, partially baffled marine type, integral engine mounts | |
Manifold | Water jacketed exhaust and intake manifold in one casting. Separate exhaust flange tapped 1 1/4 in NPT bolts to manifold with two 3/8" NC cap screws or studs at exhaust opening at rear of manifold. V drive models use same manifold with cap over rear opening and front opening machined for exhaust flange so that engine can be mounted facing backwards, as required for use of V drive. | |
Exhaust pipe | 1 1/4 in NPT (pipe thread) galvanized thick wall pipe | |
Lubrication | Full
pressure to mains, connecting rod big ends, idler gear
stud, camshaft bearings, transmission sun & planet
gear assembly Marine type fine brass mesh oil pump pickup screen surrounding pickup to retain oil in rough seas and prevent oil pump ingesting air, exterior oil pressure adjustment |
|
Water jacket cover | Removeable block water jacket plate (standard is carbon steel, stainless steel plates available from after-market suppliers) | |
Cooling system | Constant flow, 2 stage thermostat, rubber impellor water pump (later models) | |
Thermostat upper plate height | OEM
Holley 3 spring: closed (cold) .325 in / open (hot) .625
in replacement Westerbeke single spring: closed (cold) .2 in / open (hot) .8 in |
|
Thermostat housing bypass boss depth | .4 in - .5 in | |
Mechanical fuel pump pushrod size | 1.550 in long x .375 in diameter | |
Marine gear (transmission) | Paragon: combined engine / marine gear lubrication system with marine gear running in engine oil, sun and planet gear type, forward uses multiple plate clutch pack with over-centre pressure and lock, reverse uses clutch band on sun gear housing, the carrier gear assembly is pressure lubricated via a port on the crankshaft rear main bearing, the rear thrust bearing at the drive flange is splash lubricated via a bearing shield which meters the oil to and from the bearing / rear seal. | |
Reduction Gear (optional) | Single step, internal helical and pinion type, 2.04:1 ratio | |
Carburetor | Updraft
Zenith marine non-drip type carburetor, upturned air horn
with flame arrester screen: 1949 - 1968 Zenith Bendix type 61, cast-iron (adjustable main jet) 1969 - 1984 Zenith Bendix type 68, aluminum (fixed main jet) |
|
Electrical Charging System | Post 1967 12 volt DC, 35 amp Motorola marine alternator, transistorized alternator-mounted voltage regulator, 12 volt DC solenoid equipped starter (optional 50 amp Motorola marine alternator was available at extra cost) | |
Propeller rotation | Right hand (clockwise facing the rear of the propeller) | |
Propeller shaft / coupling diameter | Direct
Drive: ¾ in, 7/8 in, 1 in Reduction Drive: 1 in, 1 1/8 in V Drive: 7/8 in, 1 in |
|
Propeller
Size Note: propeller fitted must allow the engine to reach at least 1,800 rpm during hull speed / full throttle testing |
2
Blade Direct drive: 11 x 7, 12 x 6 (most common size), 12 x 7, 13 x 5 2:1 Reduction Drive: 12 x 11, 12 x 12, 13 x 10, 13 x 12, 15 x 8, 15 x 10 3
Blade (recommended for areas with severe currents, winds,
tides) |
|
Crankshaft rotation | Clockwise (right hand) viewed from rear of engine output shaft | |
Reduction gear ratio options | 2.04:1, 3.01:1 | |
V drive ratio options | 1.00:1, 1.29:1, 1.67:1, 2.0:1 | |
Torque / RPM / HP | ||
Fuel | Original specification was "standard 92 - 94 octane gasoline", later revised to "regular 90 - 94 octane" (when the specifications were written all gasoline contained lead, which was used to raise the octane rating and extend valve seat life). Modern "Regular" 87 or 89 octane non-leaded gasoline is OK as long as the compression is below 120 psi and the ignition timing is set by adjusting distributor at full cruise speed to give maximum tachometer rpm. Octane booster & lead additive is not recommended or necessary. | |
Maximum operating angle | 15° | |
Length overall | UJ: 26 ¾ in, UJR: 31 15/16 in, UJVD: 35 13/16 in | |
Height above crankshaft centreline | 13.125 in | |
Maximum width | 18.250 in | |
Offset crankshaft to propeller shaft | UJ:
0 in UJR: 1.042 in UJVD: na |
|
Base depth below centreline | 6 in | |
Weight | UJ:
310 lb UJR: 330 lb UJVD: 335 lb |
|
Firing order (#1 cylinder: flywheel end) | 1 2 4 3 | |
Valve timing | Inlet
valve opens: 5 BTDC Inlet valve closes: 50 ABDC Exhaust valve opens: 45 BBDC Exhaust valve closes: 10 ATDC |
|
Valve guide dimensions | 1.5 in long x .5 in diameter | |
Valve length | 3.685 in | |
Intake valve head diameter | 1.500 in | |
Exhaust valve head diameter | 1.030 in | |
Valve spring diameter | 1949
1967: .785 in 1966 1967: .800 in 1968 1984: .810 in |
|
Valve spring free length | 1949
1967: 1.825 in (coil bound at .760 in) 1966 1967: 1.925 in (coil bound at .800 in) 1968 1984: 2.075 in (coil bound at .810 in) |
|
Compression | 90 psi 125 psi, optimum 100 psi | |
Alternator drive ratio (through PTO gear & V belt pulley) | 1.75:1 (1 turn of engine crankshaft = 1 ¾ turn alternator) | |
Flywheel ring gear & housing dimensions | 1949
1967 (Prestolite starter): ring gear OD / flywheel
housing ID 11 in 1968 1984 (Delco starter): ring gear OD / flywheel housing ID 11.5 in |
|
Fuel consumption | Approximately 4 litres/hour (1 US gal/hour) @ 2,000 rpm under load depending on boat size & winds/currents | |
Auxiliary primary fuel filter recommendation | Filter
mesh size & type rating: 10 micron with water
separator section & metal bowl (ie Racor 320R-RAC-02) Minimum Flow Rating: 15 litre / hour |
|
Mechanical fuel pump | AC
Delco mechanical rubber diaphragm type, maximum pressure
3.0 psi Auxiliary sediment bowl with internal mesh filter |
|
Electric fuel pump | Facet
574A, 12 volts, maximum pressure 4.0 psi Internal mesh filter accessible by removing cam lock bottom cap In-line fuse 10 amp Should be fitted with oil pressure safety switch (Hobbs 76576 - 10 n.o.) to stop pump if engine stalls or ignition switch left in "on" position |
|
Pipe / Hose Sizes | Exhaust
flange: 1 1/4 in NPT - 1 1/2 in or 1 /5/8 in hose Water pump inlet: 3/8 in NPT - 1/2 in or 5/8in hose Water pump outlet: 3/8 in NPT - 1/2 in hose Fuel pump connection: 1/8 in NPT - 5/16 in OD copper pipe, double flared or 1/4 in ID hose (alcohol compatible) |
|
Design Changes | Engine Specification Updates | circa
1949: Serial #? Zenith series 61-M2AE7 cast iron carburetor with adjustable main jet Dole thermostat Auto-lite ignition Fairbanks Morse magneto (optional) Auto-lite 6 volt starter Auto-lite 6 volt generator Prestolite distributor (1Gw60032E1X) bronze gear water pump old style heat exchanger kit (optional) 5 unit control panel with mechanical tachometer, mechanical oil pressure gauge, mechanical water temperature gauge circa
1962: Serial #? circa 1963: Serial
#? circa 1964: Serial
#? circa 1965: Serial
#? circa 1967: Serial
#79476 circa 1967: Serial
#170509 circa 1967: Serial
#171514 circa 1968: Serial
#174340 circa 1969: Serial
#174802 circa 1969: Serial
#175503 circa 1970: Serial
#176500 circa 1972: Serial
#178801 circa 1975: Serial
#192787 circa 197?: Serial
#? circa 1979: Serial
#202987 circa 1980: Serial
#20? |
Wear Limit Sizes/Clearances | Bore | Std
size: 2.562 in 2.563 in .010 in oversize: 2.572 in 2.573 in .020 in oversize: 2.582 in 2.583 in |
Piston skirt clearance | .001 in - .002 in (.0015 in feeler blade to 5 lb pull) | |
Piston ring gap | .007
in - .015 in Note: ensure replacement Hastings or Ertel oil ring bottom spring end gaps are over oil drain slot in bottom of oil ring land replacement
Hastings piston rings are configured as follows: Note: Install rings with gaps staggered 120 degrees around piston. Do not locate any gaps on thrust side |
|
Piston ring side clearance | Top
(compression): .0015 in - .003 in Middle: .001 in - .0025 in Bottom (oil): .001 in - .0025 in |
|
Piston pin diameter | .6880 in | |
Piston pin rod bushing ID | .6885 in - .6900 in | |
Piston pin clearance in rod bushing (slip fit) | .0005 in - .001 in | |
Piston pin clearance in piston (push fit) | .0001 in - .0005 in | |
Oil pump drive end play | .001 in - .003 in | |
Oil pump gear backlash | .003 in - .005 in | |
Camshaft gear backlash | .002 in - .004 in | |
Idler gear backlash | .002 in - .004 in | |
Accessory gear backlash | .002 in - .004 in | |
Connecting rod big end side play on crankshaft journal | .004 in - .008 in | |
Crankshaft end play (at front main bearing) | .002 in - .003 in | |
Valve seat angle | 45° | |
Valve seat width | 1/32 in | |
Valve stem diameter | .3115 in - .312 in | |
Valve stem / guide clearance | cast
iron guides: .003 in - .004 in (OEM guides are cast iron) bronze guides in fresh water cooled engines with 180 thermostat: .0035 - .0045 in |
|
Valve guide internal diameter | .3145 in - .3165 in (see valve stem/guide clearance above) | |
Valve spring installed length - no cam lobe lift (intake & exhaust) | 1.19 in | |
Valve spring length - cam lobe full lift (intake & exhaust) | .94 in | |
Maximum cam lobe lift | .239 in | |
Valve face angle | 45° | |
Crankshaft main bearing journal | Std:
1.9880 in, +.0005 in / -.0000 in .010 in undersize: 1.9780, + .0005 in / - .0000 in .020 in undersize: 1.9680, + .0005 in / - .0000 in .030 in undersize: 1.9580, + .0005 in / - .0000 in |
|
Crankshaft rod bearing journal | Std:
1.5625 in, +.0000 in / .-.0005 in .010 in undersize: 1.5525 in, + .0000 in / - .0005 in .020 in undersize: 1.5425 in, + .0000 in / - .0005 in .030 in undersize: 1.5325 in, + .0000 in / - .0005 in |
|
Crankshaft marine gear sun & planet carrier bearing journal | 1.869 in, +.0005 in / .-.0000 in | |
Main bearing clearance | .001 in - .0025 in | |
Rod bearing clearance | .001 in - .0025 in | |
Rod big end diameter | 1.665 in | |
Rod side play on crankshaft journal | .004 in - .008 in | |
Rod installation | Cylinder no stamped on rod big end towards camshaft, #1 rod at front (flywheel end) on #1 piston, #2 rod second from front on #2 piston, etc | |
Camshaft bearing journal | 1.3745 in, +.0005 in / -.0000 in | |
Camshaft bearing clearance | .0015 in - .0025 in (line ream after installation) | |
Piston installation | Arrow on crown pointing to rear (towards marine gear), vertical expansion slot on skirt facing away from camshaft, #1 piston at front (flywheel end), #2 piston second from front, etc | |
Piston
skirt diameter (bottom of skirt near expansion slot at
right angles to pin) Note: pistons are not round when at room temperature because they are cam ground oval so they expand to round when at engine running temperature |
Std:
2.560 in .010 in oversize: 2.570 in .020 in oversize: 2.580 in .030 in oversize: 2.590 in |
|
Front main bearing width: | 1.620 in | |
Idler gear shaft diameter | .8766 in, +.0000 in / -.0002 in | |
Idler gear bushing id | .8772 in - .8777 in | |
Camshaft bushing inner diameter | 1.376 in 1.377 in | |
Oil pump drive end play | .001 in - .003 in | |
Distance from top of cylinder head spark plug thread to cylinder block deck | .980 in - 1.175 in | |
Distance from bottom of spark plug thread to cylinder head surface | .480 in - .625 in, average approximately .525 in | |
Cylinder head combustion chamber volume with piston at TDC (including spark plug hole) | 40 cc - 51 cc, average approximately 50 cc | |
Cylinder swept volume + combustion chamber volume with piston at BDC (including spark plug hole) | 313.5, average approximately 314 cc | |
Maximum cylinder bore ovality | .002 in | |
Maximum cylinder bore taper | .008 in | |
Maximum cylinder head warp | .006 in | |
Valve spring compressed length (full lift of camshaft lobe) | ?? in | |
Valve spring installed height (with valve clearance) | ?? in | |
Coil primary resistance | Internal
ballast type: 3 - 4 ohm (standard coil) (Note: External ballast type (.5 - 1 ohm) is not necessary or recommended. If fitted an external ballast resistor (2 - 3 ohm) must also be installed in series.) |
|
Starter
solenoid current draw Starter winding currrent draw |
approximately
20 amps approximately 150 amps |
|
Valve spring pressure | ?? | |
Intake manifold vacuum | Idle:
16 in Hg 2,000 rpm under load: 14 in Hg |
|
Exhaust system back pressure (measured after water injection point) | 3 psi / 3 in Hg maximum at full load | |
Crankcase sump flow (indicating piston ring and valve guide combustion blow-by) | New
engine: approximately .25 cfm/+.5" H2O/?psi at full
speed / load Worn engine: approximately .50 cfm/+?H2O/?psi at full speed / load |
|
Distributor rotor position @ TDC#1 (compression stroke) | #1 terminal at 09:00 viewed from front of engine (pointing to extrusion on distributor plate which fits into slot in cap and is also at 09:00) | |
Adjustments | Ignition timing | Static:
No advance = 0° BTDC / Full advance = 17°
BTDC Dynamic: <700 rpm = 0° BTDC / >1,800 rpm = 17° BTDC |
Valve tappet clearance | Intake:
.008 in hot, .010 in cold Exhaust: .010 in hot, .012 in cold |
|
Distributor dwell | Prestolite:
38° Delco: 31° - 34° |
|
Distributor points gap | Prestolite:
.018 in - .020 in Delco: .025 in magneto: .014 in - .018 in |
|
Spark plug gap | .035 in | |
Alternator belt tension | 3/8 in depression between centres, pressing firmly with one finger | |
Oil pressure relief valve | 35 psi at 2,000 rpm (or top cruising speed) hot | |
Paragon marine gear forward clutch pack | approximately 30 - 50 ft lb torque on shift shaft to force 3 pressure plate arms over bulge in throw-out bearing | |
Paragon marine gear rear band | with gear lever in neutral tighten reverse band adjusting nut (holes in flats so a nail or pick can be used as an adjusting tool) until output shaft turns stiffly, then back off 1 - 2 rotations until shaft turns freely | |
Machining Specs | Cylinder head & manifold grinding finish | #125 RMS / #112 RA |
Cylinder bore honing finish | Hone
finish, 60° crosshatch pattern (Std size bore 2.562 in - 2.563 in) |
|
Cylinder block deck & manifold finish | #90 RMS / #80 RA | |
Lubricants | Lubricating oil | Depending on installation angle of engine: 4 litres 6 litres at temperatures over 10°C / 50°F use SAE 10-30, 10-40, 15-40, SJ or CH-4 rating, to full mark on dip stick (different dip sticks for UJ, UJR, UJVD) |
V Drive Oil | .5 litre of SAE 80W90 hypoid oil (SAE 30 motor oil is also acceptable) | |
Water pump grease | Waterproof grease (white lithium, boat trailer wheel bearing grease, etc) | |
Fastener
Torque Note: Lubricate threads and base of bolt head / nut with oil |
Cylinder head stud nuts | 35
ft lb, 3 stages: 10 ft lb / 25 ft lb / 35 ft lb, use shop
manual torquing diagram or torque from centre of head out
to ends. Retorque hot to 35 ft lb after 1 hour of
running. Be careful not to exceed 35 ft lb. On older
engines stud pull is a common problem. If a stud pulls
the threads out of the block remove the head and install
a 3/8" NC thread repair insert. Note: install cylinder and manifold studs into block with gasket cement or Loctite "red", and coat sides of studs with Never-Seize to prevent studs from seizing to head or manifold |
Connecting rod bolt nuts | 25 ft lb | |
Flywheel stud nuts | 35 ft lb | |
Main bearing stud nuts | 60 ft lb | |
Manifold stud nuts | 30 ft lb | |
Spark plugs | 30 ft lb (apply Never-Seize to threads) | |
Valve cover cap screws | 20 in / lb (with cork gasket) | |
Flywheel cover cap screws | 85 in / lb | |
Idler Gear stud nut | 35 ft lb (use red Loctite) | |
Oil pump cover screw | 12 ft lb (use blue Loctite) | |
Oil pan & block 5/16" cap screws | 18 ft lb | |
Transmission output shaft flange nut | 60 ft lb (use tab lock washer) | |
Crankshaft channeled gear retaining bolt | 25 ft lb (use blue Loctite) | |
Service Parts | Spark plugs | Specified
plug: Champion #871 (old number RJ8C) Recommended plug (slightly hotter,
helps stop plug sooting): Other plugs used
(nominal Champion RJ8C equivalents): |
Contact Breaker (points) | Prestrolite
Distributor: Echlin CS-709 Delco
Distributor: |
|
Capacitor (Condenser) | Prestolite
Distributor: Echlin AL38 Delco
Distributor: |
|
Rotor | Prestolite
Distributor: Echlin AL58 Delco
Distributor: |
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Cap | Prestolite
Distributor: Echlin AL91 Delco
Distributor: |
|
Coil | Prestolite
or Delco Distributor: Delco 070FLX Niehoff DR-180 (standard) Niehoff UN171 (epoxy heavy duty) Standard UC12 Specifications: |
|
Distributor
|
Prestolite distributor
(1Gw60032E1X) Delco Remy distributor (#1112446 - 2G11/6C16/3HI8) & coil |
|
HT Leads (spark plug wires) | Atomic
Four Engine Service A4HTset Specifications: |
|
Generator | Prestolite
6 or 12 volt generator: obsolete - substitute Delco alternator below: Motorola alternator: Specifications: |
|
Starter | Prestolite: MBG4129 (solenoid Wilson 60-01-6029) Delco: Specifications: Note: Prestolite and Delco starters use different flywheel ring gears |
|
Alternator belt | Dayco:
11A0635 (10A0635 also used) Gates: 11A0635 (10A0635 also used) |
|
Engine coolant hoses | 1/2"
id automotive heater hose & stainless steel gear
clamps water pump
outlet to block water plate "T": 10.5 in |
|
Temperature Sensor (electric) | SW
280ED-F General Marine GEN26630 Aqua Power AP1943 Faria FAR90405 Specification: |
|
Oil
Pressure Sensor (electric) |
SW
279A General Marine GEN24880 Faria FAR90512 Specification: |
|
Seawater pump belt (pump over starter) | Dayco:
11A770 Gates: 11A770 |
|
OEM
flange mounted water pump - gear driven off PTO unit Used as sea water pump when engine is raw water cooled with no heat exchanger. When heat exchanger is fitted used as engine coolant pump, except when electric pump is fitted, when it is used as sea water pump and electric pump is used as an engine coolant pump. |
After
1969 OEM pump was Oberdorfer 202M3 (2 US gal / minute, 15
psi max @ 1,000 rpm) Cam thickness .105 in (half cam) Note: 202M3 is usually upgraded to
Oberdorfer 202M7 when rebuilt or replaced by installing
M7 cam. M7 was used on older diesels Impellor: |
|
Sea water pump used with heat exchanger: belt driven off pulley on end of crankshaft at flywheel, driven directly off end of crankshaft, belt driven using alternator drive belt, or electric motor pump | Sherwood
R30G / Jabsco 2620-1001 / Oberdorfer 201M (or any pump
with a continuous capacity of 6 US gal / minute @ 1,800
rpm and a rpm rating of at least 3,000 rpm) water pump / crankshaft pulley ratio: 1:1 |
|
Carburetor Jets | 1948
1968 Zenith 61-M2AE7: main jet #24, Zenith C52-6-24 & adjustable needle assembly idle jet #10, Zenith C55-6-10 (.019 in drill size) well vent jet #22, Zenith C77-18-22 (.043 in drill size) main discharge nozzle #50, Zenith C66-26-1-50 1969 1984 Zenith Bendix
68-7: |