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Home›Engines›Generac GH-220

Generac GH-220 Engine

The Generac GH-220 is a naturally aspirated engine rated at 3600 rpm. It powers generator sets from Generac, including the QuietPact 40G and QuietPact 40LP.

Also known as: Generac GH-220

3600 rpm
Rated speed
On this pageSpecsGenerator setsMaintenanceFAQTorque & specsProcedures

Engine specifications

Aspirationnaturally aspirated
Rated speed3600 rpm

Generator sets powered by this engine

2
Generac QuietPact 40GGenerac QuietPact 40LP

How to read your Generac engine serial & model number →

Maintenance schedule

ItemSpecCapacityPart #Interval
Oil filter—
Spark plugChampion RC14YC (or equivalent), gap 0.030 inch (0.76mm)—

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

Service specifications

16
TypeItemValueUnitCondition
ClearanceExhaust valve clearance0.0018-0.003inch (0.046-0.07 mm)engine at room temperature, piston at TDC compression stroke
ClearanceIntake valve clearance0.001-0.0022inch (0.03-0.056 mm)engine at room temperature, piston at TDC compression stroke
Other7.5 Amp Fuse (F1)7.5ampengine controller circuit board fuse
OtherBattery charge circuit series resistor1 ohm, 25 wattgrounded side of battery charge circuit (R1)
OtherField boost circuit resistor47 ohm, 2 wattin series with field boost diode to Pin 13 of engine controller board
PressureCylinder leak-down tester regulated pressure80psiair source of at least 90 psi; 20 percent leakage normally acceptable
PressureMinimum allowable compression pressure, cold engine60psiGH-220 cold engine
PressureMinimum oil pressure (low oil pressure switch check)10psiengine running, switch contacts should open above this pressure
ResistanceRotor winding resistance, slip ring to slip ring12.72 to 14.73ohms
ResistanceStator power windings resistance (11 & 22, and 33 & 44)0.468 to 0.542ohm
SpeedNo-load governed engine speed3720rpmno electrical load connected; yields ~62 Hz output
SpeedRated operating speed3600rpm60 Hz output, 2-pole rotor
TemperatureOil temperature switch trip point305°F (151°C)protective shutdown threshold
TorqueRocker arm jam nut72inch-pounds
VoltageNo-load AC output voltage adjustment target124VACfrequency set to 62.5 Hz, no load, adjusted via voltage regulator pot
VoltageResidual voltage induced in stator (no field boost)7 to 12VACrotor residual magnetism only

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

Procedures

5
Test 35 - Check Valve Adjustment adjustment

Tools: feeler gauge, 8mm allen wrench, crow's foot torque wrench

  1. Adjust valve clearance with engine at room temperature, piston at TDC of compression stroke (both valves closed)
  2. Alternatively, position intake valve fully open to adjust exhaust valve, and exhaust valve fully open to adjust intake valve
  3. Loosen rocker arm jam nut; turn pivot ball stud with 8mm allen wrench while checking clearance with feeler gauge
  4. Tighten rocker arm jam nut to specified torque with crow's foot while holding pivot ball stud
  5. Recheck valve clearance after tightening to ensure it did not change
  6. Install new rocker arm cover gasket and reinstall cover with four screws; install oil breather tube
Voltage Adjustment Procedure adjustment

Tools: voltmeter

  1. Set frequency to 62.5 Hertz with no load on the generator
  2. Slowly turn the voltage adjust pot on the voltage regulator until 124 VAC is measured
Test 38 - Check Engine/Cylinder Leak Down Test / Compression Test diagnostic

Tools: cylinder leak down tester, compression gauge

  1. Remove spark plug and valve cover
  2. Rotate crankshaft to TDC with both valves closed; lock flywheel
  3. Attach cylinder leak down tester adapter to spark plug hole
  4. Connect air source of at least 90 psi; adjust regulated pressure to 80 psi
  5. Read cylinder pressure gauge; 20 percent leakage is normally acceptable
  6. Listen for air escaping at carburetor (intake valve), exhaust (exhaust valve), or breather (piston rings)
  7. For compression check, insert compression gauge in spark plug hole and crank engine until pressure stops increasing
Test 39 - Check Oil Pressure Switch diagnostic

Tools: VOM, oil pressure gauge

  1. Check engine oil level, replenish to FULL mark if necessary
  2. Set VOM to Rx1 scale and zero meter
  3. Connect meter leads across switch terminals with engine shut down; should read continuity
  4. Crank engine; meter should read infinity once oil pressure opens switch contacts
  5. If contacts do not open, remove switch and connect oil pressure gauge in its place; start engine and measure pressure
Test 40 - Test Oil Temperature Switch diagnostic

Tools: VOM, thermometer

  1. Remove Wire No. 85 from switch terminal and start generator to isolate the fault
  2. Remove switch and place sensing tip into oil with a thermometer
  3. Connect VOM test leads across switch terminals; should read infinity
  4. Heat oil; at approximately 305°F (151°C) switch contacts should close and meter should read continuity

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 Generac GH-220 engine?

The Generac GH-220 powers 2 generator set(s), including Generac QuietPact 40G, Generac QuietPact 40LP.