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Hercules G/GTA4800 Engine

The Hercules G/GTA4800 is a 6-cylinder nat. asp. engine rated at 1800 rpm. It powers generator sets from Hercules, including the G4800.

Also known as: HERCULES G/GTA4800

Cylinders

1800 rpm

Rated speed

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Procedures

Engine specifications

Cylinders	6
Aspiration	NAT. ASP.
Rated speed	1800 rpm

Generator sets powered by this engine

Hercules G4800

Common problems

SYSTEM HAS WEAK OR NO OUTPUT
Fix: Check stator (9) resistance - replace if defective - see 5.0 below. Check circuit board assembly (27) - replace if defective - see pg. 11.
ONE OUTPUT DOES NOT FIRE
Fix: Check that the 2-lead pick-up coil connector is fully plugged into the circuit board receptacle. If not, replace pick-up coil assembly (26a) - see pg. 11.
Fuel System - Fuel Pump Malfunction - 2, Ignition System - Spark Plug Misfire - 8 F 2&8 4
Engine - Cylinder C - Spark Plug Misfire - 2 E Cc 2
Distributor - Distributor Timing Off - 6 D D 6
Cylinder C - Excessive Spark Plug Wear - 3 Cc E 3
Battery Fault - 5 B F 5

Compiled from service & troubleshooting documentation across every generator set that uses the Hercules G/GTA4800.

Maintenance schedule

Item	Spec	Part #	Interval
Air filter		—	125 hr
Fuel filter		—	125 hr
Oil filter		—	125 hr
Battery	12V 800 CCA @ 0° F, 24V 400 CCA @ O° F	—
Belt		—	125 hr
Coolant		—
Oil	SAE#2 for li-1/2" Clutch, SAE#1 for 14" Clutch	—	125 hr
Spark plug	Champion: '42095 Check at 250 Hrs, Change at 500 Hrs	—	500 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Months	Notes
Cylinder head nuts	Test	2 hr		First service — Retorque after two hours of service on new or reconditioned engine
Valve tappet clearance	Adjust	500 hr		First service — Reset after two hours of service on new or reconditioned engine
Crankcase oil	Change	125 hr		First service — New or reconditioned engine; suggested first change each 50 hours for first 100 hours
Fan belts	Adjust	100 hr		Inspect and adjust if loose
Fuel supply tank	Clean	100 hr		Inspect; wash with clean fuel oil if necessary; remove air from fuel filters
Radiator	Clean	100 hr		Inspect; clean if clogged or scale formation
Accessory drive belts	Adjust	125 hr		Tighten
Crankcase breather	Clean	125 hr
Oil filter	Change	125 hr
Primary fuel filter	Replace	125 hr		Replace primary fuel filter only
Radiator air passages	Check	125 hr		Clean if dirty or restricted
Alternator	Lubricate	400 hr		Three to four drops engine oil
Starting motor	Lubricate	400 hr		If equipped with oilers
Air filter	Change	500 hr		Change air filter
Engine	Inspect	500 hr		Loose connections, leaks in oil/fuel/water, cracks, free action of moving parts
Fuel pump timing	Adjust	500 hr		Check and adjust if necessary
Governor and throttle linkage	Adjust	500 hr
Injector nozzles	Clean	500 hr		Clean, inspect and set if loss of performance or exhaust smoke density indicates a problem
Air cleaner primary element	Replace	1000 hr	12 mo	Replace yearly, every 1000 hours, or after 10 cleanings, whichever comes first

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Camshaft bearing clearance	.001 - .003	in.
Clearance	Camshaft end thrust	.006 - .010	in.
Clearance	Connecting rod bearing	.0014 - .0044	in.
Clearance	Connecting rod side clearance	.007 - .013	in.
Clearance	Crank gear to crankshaft	.0003 - .0013	in.
Clearance	Crankshaft end clearance	.010 - .015	in.
Clearance	Crankshaft main bearing clearance	.0018 - .0048	in.
Clearance	Piston pin to connecting rod bushing	.0016 - .002	in.
Clearance	Piston pin to piston	.0002 - .0006	in.
Clearance	Piston to cylinder clearance, 3 ring piston part #380045, bottom of skirt	.006 - .0085	in.
Clearance	Piston to cylinder clearance, 3 ring piston part #380045, top of piston	.017 - .0215	in.
Clearance	Piston to cylinder clearance, 4 ring piston part #380407, bottom of skirt	.007 - .0095	in.
Clearance	Piston to cylinder clearance, 4 ring piston part #380407, top of piston	.039 - .0425	in.
Clearance	Rocker arm to rocker arm shaft	.002 - .004	in.
Clearance	Side clearance 2nd ring, 3 ring piston part #380045	.0035 - .0055	in.
Clearance	Side clearance 2nd ring, 4 ring piston part #380407	.001 - .0025	in.
Clearance	Side clearance 3rd ring, 4 ring piston part #380407	.0025 - .0035	in.
Clearance	Side clearance oil control ring, 3 ring piston part #380045	.001 - .003	in.
Clearance	Side clearance oil control ring, 4 ring piston part #380407	.001 - .003	in.
Clearance	Side clearance top ring, 3 ring piston part #380045	.0035 - .0055	in.
Clearance	Side clearance top ring, 4 ring piston part #380407	.001 - .0025	in.
Clearance	Top of cylinder block to top of piston protrusion	.01185 - .02775	in.
Clearance	Top of liner cylinder block protrusion	.0005 - .004	in.
Clearance	Valve lash exhaust	.025	in.	Hot and cold
Clearance	Valve lash intake	.010	in.	Hot and cold
Clearance	Valve stem to guide exhaust	.0048 - .0056	in.
Clearance	Valve stem to guide intake	.0021 - .0039	in.
Gap	2nd ring gap at 4.5625, 3 ring piston part #380045	.016 - .026	in.
Gap	2nd ring gap at 4.5625, 4 ring piston part #380407	.013 - .023	in.
Gap	3rd ring gap at 4.5625, 4 ring piston part #380407	.013 - .023	in.
Gap	Oil control ring gap at 4.562, 3 ring piston part #380045	.016 - .026	in.
Gap	Oil control ring gap at 4.562, 4 ring piston part #380407	.016 - .026	in.
Gap	Top ring gap at 4.5625, 3 ring piston part #380045	.016 - .026	in.
Gap	Top ring gap at 4.5625, 4 ring piston part #380407	.013 - .023	in.
Pressure	Fuel nozzle pressure, new	3100	lbs. per sq. in.
Torque	Bellhousing nuts	20 then 45	ft. lbs.	Step 1: 20 ft lbs; Step 2/3: 45 ft lbs
Torque	Camshaft gear to camshaft nut	275 - 300	ft. lbs.
Torque	Connecting rod bolt	115 - 120	ft. lbs.
Torque	Connecting screw (fuel line) (Roosa Master)	235 - 240	in. lbs.
Torque	Crankshaft damper to pulley cap screws	30 - 35	ft. lbs.
Torque	Crankshaft pulley assembly retaining bolt	225 - 250	ft. lbs.
Torque	Cylinder head cover attaching	3 - 5	ft. lbs.
Torque	Cylinder head nuts	110	ft. lbs.	Step 1, cold
Torque	Cylinder head nuts	130	ft. lbs.	Step 2, cold
Torque	Cylinder head nuts	157	ft. lbs.	Step 3, cold
Torque	Exhaust manifold nuts	20 - 25	ft. lbs.
Torque	Flywheel housing to cylinder block nuts	40 - 45	ft. lbs.
Torque	Flywheel to crankshaft bolt	115 - 120	ft. lbs.
Torque	Fuel line nuts at fuel pump (Bosch)	20 - 25	ft. lbs.
Torque	Fuel nozzle securing bolts	25 - 30	ft. lbs.
Torque	Fuel pump attaching nut (injection pump to adapter)	35 - 40	ft. lbs.
Torque	Injection nozzle hold down	12 - 15	ft. lbs.
Torque	Intake manifold nuts	20 - 25	ft. lbs.
Torque	Main bearing cap bolts	135 - 140	ft. lbs.
Torque	Nut - Model DM fuel injection pump drive gear	150	ft. lbs.
Torque	Oil pump attaching bolts	48 - 54	ft. lbs.
Torque	Oil pump drive gear nut	50	ft. lbs.
Torque	Rocker arm shaft bracket nut	30 - 35	ft. lbs.
Torque	Vibration damper to crankshaft pulley	30 - 35	ft. lbs.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Capacity	Notes
Coolant	Clean water or antifreeze solution		7.5 Gal (including radiator)	Use good commercial neutralizer; do not use oil, fuel oil or kerosene in cooling solution
Engine oil	SAE 10W	API CC or CD (MIL-L-2104B or C)	22.0 Qts (w/filter)	Single viscosity, low ash oil; ambient -10 to 30 F
Engine oil	SAE 15W-40	API CD		Multigrade oils with CD Classification only; ambient -10 F and up
Engine oil	SAE 20 - 20W	API CC or CD		Ambient 30 to 60 F
Engine oil	SAE 20 Detergent oil, Series No. 1			Break-in oil for new engine; use for at least 50 hours; change each 25 hours
Engine oil	SAE 30	API CC or CD		Ambient 40 F and up
Fuel	Diesel fuel oil	Flash point 125 F minimum; carbon residue 0.35 percent maximum; water and sediment 0.10 percent by volume maximum; ash 0.02 percent by weight maximum; distillation 90 percent point 640 maximum/540 minimum; viscosity at 100 F 2.0 centistokes minimum to 4.3 centistokes maximum; sulphur 1.0 percent maximum; cetane number 45 minimum		Must be clean, completely distilled, stable and noncorrosive; cloud point should be 10 F below lowest expected fuel temperature

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Installing And Timing Roosa DM Pump adjustment

Tools: Torque wrench

Spot vibration damper at proper degree mark before TDC No. 1 compression.
Install new O-ring seal on pump attaching flange.
Remove timing hole cover; rotate pump until timing marks register.
Install pump to drive gear, aligning keyway.
Install lockwasher and nuts on attaching studs.
Install flat washer and nut on pump shaft; torque to 150 ft lbs.
Recheck timing.
Install drive gear cover plate and timing hole cover.

Priming The Fuel System -- Air Lock Trouble maintenance

Loosen fuel filter vent cocks.
Allow fuel from tank to flow into filter until solid fuel comes from vent cocks.
Close vent cocks.
Crank engine if necessary to permit priming pump to draw fuel.

Starting The Engine The First Time operation

Fill fuel tank with suitable fuel oil; bleed air from lines and filter.
Fill cooling system with clean water or antifreeze.
Fill crankcase to full mark with lubricating oil.
Turn engine over three or four times with starter.
Start engine by operating starting button.
Allow engine to run several minutes before applying load.

To Install The Bellhousing repair

Install new bellhousing gasket to cylinder block.
Check mounting dowels tight and in good condition.
Install bellhousing and torque nuts in sequence.
Install rear motor support screws.
Install flywheel.
Install clutch or torque converter.

To Install The Connecting Rods repair

Assemble connecting rod and piston; insert retaining rings.
Inspect crankshaft and polish if rough.
Install piston rings.
Turn crankshaft to correct position.
Apply lubricating oil to bores, pistons, rings, pin.
Space piston rings so no two slots align.
Compress rings and push piston into bore.
Install bearing shells, cap, tighten cap screws, check side movement.

To Install The Flywheel And Indicate repair

Tools: Dial indicator

Reverse removal instructions.
Use indicator to check pilot bore concentricity.
Attach indicator to check flywheel face.
Install starting motor.
Install clutch and transmission.

To Remove The Bellhousing repair

Remove clutch or power take-off mechanism.
Remove flywheel.
Support rear of crankcase.
Remove rear motor support screws.
Remove bellhousing attaching stud nuts.
Pull bellhousing away from engine.

To Remove The Camshaft repair

Remove fan blade and belts.
Remove fan drive pulley nut, pulley, and vibration damper.
Remove gear cover.
Remove rocker arm covers, rocker arms, and push rods.
Remove lube oil filters and cooler, and fuel oil filter.
Remove side cover plates and lift out tappets in order.
Remove thrust plate attaching screws and pull camshaft forward.

To Remove The Connecting Rods repair

⚠ Keep rod caps and bearings together.

Drain radiator and engine block.
Remove thermostat housing, thermostat, and water manifolds.
Disconnect air cleaner hose and exhaust pipe.
Disconnect fuel lines and remove from pump and nozzle holders.
Remove cylinder head covers, rocker arms, and push rods.
Remove cylinder head nuts and lift cylinder head.
Remove oil pan, oil pump, lines, and piston oil spray nozzles.
Scrape carbon and remove rod caps and pistons.

To Remove The Cylinder Head repair

⚠ Do not pry on contact surfaces.

Drain radiator and remove thermostat housing, hoses, water manifolds.
Disconnect water temperature gauge thermocouple.
Disconnect exhaust pipe and air cleaner.
Remove fuel lines from nozzles.
Remove cylinder head covers, rocker arms, push rods.
Remove cylinder head nuts and lift heads.

To Remove The Flywheel repair

Tools: Lady-foot pry bar

Disconnect and remove transmission and clutch or converter.
Fabricate 1/2 x 20 x 4 in guide bolt.
Remove one flywheel bolt and install guide bolt.
Remove balance of bolts.
Use pry bar if necessary to pull flywheel from crankshaft.

To Replace The Cylinder Head repair

⚠ Do not retorque hot.

Tools: Torque wrench

Clean carbon deposits and contact surfaces.
Install new cylinder head gaskets with fire ring and grommet.
Place cylinder heads and valve assembly on block.
Tighten head nuts evenly from center to ends.
Install push rods and rocker arms.
Adjust valve tappets.
Install cylinder head cover with new gasket.
Connect fuel lines, thermostat, hoses, air cleaner, exhaust.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Common questions

Which generators use the Hercules G/GTA4800 engine?

The Hercules G/GTA4800 powers 1 generator set(s), including Hercules G4800.

How often should you change the oil in the Hercules G/GTA4800?

The Hercules G/GTA4800 oil change interval is every 125 hours.

What is a common problem with the Hercules G/GTA4800 engine?

A commonly reported issue on generators using the Hercules G/GTA4800 is: SYSTEM HAS WEAK OR NO OUTPUT. Fix: Check stator (9) resistance - replace if defective - see 5.0 below. Check circuit board assembly (27) - replace if defective - see pg. 11..