Home›Engines›General Motors 8.1L

General Motors 8.1L Engine

Name: General Motors 8.1L Engine
Brand: General Motors

The General Motors 8.1L is a 8.1 L 8-cylinder natural aspiration engine rated at 1500 rpm. It powers generator sets from General Motors, Kohler and SDMO, including the 8.1L Powertrain, 100REZG, G100 and G110. It holds 10 L (2.6 gal) of oil and 10 L (2.6 gal) of coolant.

Also known as: 8.1L, GM 8.1L

Part of the General Motors 8.1L engine family — 2 variants share parts & fitment.

8.1 L

Displacement

Cylinders

1500 rpm

Rated speed

10.0 L

Oil capacity

On this pageSpecs Generator sets Maintenance FAQ Torque & specs Wiring

Engine specifications

Oil capacity	10.0 L
Coolant capacity	10.0 L
Displacement	8.1 L
Cylinders	8
Aspiration	Natural Aspiration
Rated speed	1500 rpm

Generator sets powered by this engine

Shared across brands: General Motors, Kohler, SDMO

General Motors 8.1L PowertrainKohler 100REZG SDMO G100 SDMO G110 SDMO G125U SDMO G130

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Replace air filter		—	500 hr
Fuel filter	Replace fuel filter		—	1000 hr
Oil filter	Replace oil filter		1.836	250 hr	buy
Battery			—
Belt	Drive Belt Tensioner		374176		Amazon eBay
Coolant	Change coolant and water pump	29.9	—	1000 hr
Coolant filter			—
Oil	Change oil and filter	7.1	—	250 hr
Spark plug	Replace spark plugs		2.270	10000 hr	buy

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

Service specifications

Type	Item	Value	Unit
Other	10 in. weld flange bolt circle diameter B	361.95	mm (14.25 in.)
Other	10 in. weld flange outside diameter C	406.4	mm (16.0 in.)
Other	10 in. weld flange quantity of bolts / bolt hole diameter D	12, 25.40	mm (1.00 in.)
Other	12 in. weld flange bolt circle diameter B	431.80	mm (17.00 in.)
Other	12 in. weld flange outside diameter C	482.6	mm (19.0 in.)
Other	12 in. weld flange quantity of bolts / bolt hole diameter D	12, 25.40	mm (1.00 in.)
Other	14 in. weld flange bolt circle diameter B	476.25	mm (18.75 in.)
Other	14 in. weld flange outside diameter C	533.4	mm (21.0 in.)
Other	14 in. weld flange quantity of bolts / bolt hole diameter D	12, 28.58	mm (1.13 in.)
Other	16 in. weld flange bolt circle diameter B	539.75	mm (21.25 in.)
Other	16 in. weld flange outside diameter C	596.9	mm (23.5 in.)
Other	16 in. weld flange quantity of bolts / bolt hole diameter D	16, 28.58	mm (1.13 in.)
Other	18 in. weld flange bolt circle diameter B	577.85	mm (22.75 in.)
Other	18 in. weld flange outside diameter C	635.0	mm (25.0 in.)
Other	18 in. weld flange quantity of bolts / bolt hole diameter D	16, 31.75	mm (1.25 in.)
Other	20 in. weld flange bolt circle diameter B	635.00	mm (25.00 in.)
Other	20 in. weld flange outside diameter C	698.5	mm (27.5 in.)
Other	20 in. weld flange quantity of bolts / bolt hole diameter D	20, 31.75	mm (1.25 in.)
Other	5 in. weld flange bolt circle diameter B	215.90	mm (8.50 in.)
Other	5 in. weld flange outside diameter C	241.30	mm (9.50 in.)
Other	5 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	6 in. weld flange bolt circle diameter B	254.0	mm (10.0 in.)
Other	6 in. weld flange outside diameter C	279.4	mm (11.0 in.)
Other	6 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	8 in. weld flange bolt circle diameter B	298.45	mm (11.75 in.)
Other	8 in. weld flange outside diameter C	342.9	mm (13.5 in.)
Other	8 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	Weld flange angle A (10, 12, 14 in. nominal pipe size)	30	deg.
Other	Weld flange angle A (16, 18, 20 in. nominal pipe size)	22.5	deg.
Other	Weld flange angle A (5, 6, 8 in. nominal pipe size)	45	deg.

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

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		12-Lead		Alternator Reconnections diagram ADV-5875B-M (page 16)
		4-Lead		Alternator Reconnections diagram ADV-5875A-M (page 15)

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

Parts cataloged across the General Motors 8.1L family

Part #	Description	Category
374176	Drive Belt	belt
NGE012014	Radiator Fan Shroud Bolts	bolt
375105	Clutch Pilot Bearing Removal (C/K/C3500HD)	clutch_pilot_bearing_removal
470627	Clutch Pilot Bearing Removal (Medium Duty)	clutch_pilot_bearing_removal
373133	Clutch Pilot Bearing Removal Tools Required	clutch_pilot_bearing_removal_tools_required
640014	Crankshaft Balancer Removal Steps	crankshaft_balancer_removal_steps
640013	Crankshaft Balancer Removal Tools Required	crankshaft_balancer_removal_tools_required
638596	Cylinder Head and Components	cylinder_head_and_components
638608	Engine Crankshaft and Components	engine_crankshaft_and_components
470599	Engine Flywheel Housing Removal (Medium Duty with AT)	engine_flywheel_housing_removal
470572	Engine Flywheel Removal (C/K/C3500HD with AT MT1)	engine_flywheel_removal
470576	Engine Flywheel Removal (Medium Duty with MT)	engine_flywheel_removal
677814	Engine Flywheel Removal (C3500HD with AT M74)	engine_flywheel_removal
679414	Engine Flywheel Removal (C/K with MT)	engine_flywheel_removal
677764	Engine Identification Number	engine_identification_number
1052367	Engine Oil Supplement Lubricant	fluid
9985770	MAP Sensor Seal Lubricant	fluid
GM16430	Sealer, oil pan / Sealant, Loctite	fluid
GM18888	Sealer, crankshaft rear main bearing	fluid
GM18933	Sealer, camshaft bearing hole plug	fluid
GM18934	Grease, heavy duty multipurpose	fluid
638592	Flywheel Housing Adapter, Medium Duty with Manual Transmission	flywheel_housing_adapter
GM18951	Gasket, engine front cover, also part of 76	gasket
GM18963	Gasket, water pump	gasket
GM18964	Gasket, engine coolant crossover	gasket
GM19009	Gasket, oil pan	gasket
GM18967	Hose, therm bypass includes hose clamps	hose
638602	Intake Manifold and Components	intake_manifold_and_components
638616	Lower Engine Block and Components	lower_engine_block_and_components
GM16703	Filter, oil	oil_filter
470639	Oil Level Indicator and Tube Removal (C/K/C3500HD)	oil_level_indicator_and_tube_removal
470666	Oil Level Indicator and Tube Removal (G)	oil_level_indicator_and_tube_removal
1051396	Engine Oil Supplement Lubricant	other_service
1052942	Crankshaft Rear Bearing Cap Sealant	other_service
12377901	Camshaft Rear Bearing Hole Plug Sealant	other_service
LG199	Home Maintenance Kit	other_service
GM18990	Pump, oil with screen	pump
GM19027	Pump kit, water (incl. 31, 82, 83, 85, 105)	pump
470515	Repair Instructions - Draining Fluids and Oil Filter Removal	repair_instructions
GM16576	Seal, oil pan drain plug (part of item 63)	seal
GM18971	Seal, crankshaft rear oil	seal
GM18972	Seal, crankshaft front oil	seal
290090	Switch, low water temperature	sensor
GM18906	Sensor, knock	sensor
GM18952	Sensor, crankshaft position (includes 123)	sensor
GM19004	Sensor, camshaft position (2001 GM engines / GM model year 2003 and older)	sensor
GM24739	Sensor, camshaft position (2002 and 2003 GM engines)	sensor
GM51539	Sensor, camshaft position (2004-- GM engines)	sensor
GM75077	Sensor, Cm/Shf Posn (GM model year 2004 and newer)	sensor
GM42165	Thermostat, block heater 49C--60C (120F--140F)	thermostat

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the General Motors 8.1L?

The General Motors 8.1L engine has an oil capacity of 10.0 liters.

What is the displacement of the General Motors 8.1L?

The General Motors 8.1L has a displacement of 8.1 liters with 8 cylinders.

Which generators use the General Motors 8.1L engine?

The General Motors 8.1L powers 6 generator set(s), including General Motors 8.1L Powertrain, Kohler 100REZG, SDMO G100, SDMO G110, SDMO G125U.

How often should you change the oil in the General Motors 8.1L?

The General Motors 8.1L oil change interval is every 250 hours.