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Engine Mechanical (H4DOTC) (Except Sti): Specifications Subaru Impreza GH

Mechanical 6 illustrations ~282 words

SPECIFICATION

EngineModel2.5 L
Cylinder arrangementHorizontally opposed, liquid cooled, 4-cylinder, 4-stroke gasoline engine
Valve system mechanismBelt driven, double overhead camshaft, 4-valve/cylinder
Bore x StrokeMm (in)99.5 x 79.0 (3.92 x 3.11)
DisplacementCm 3 (cu in)2,457 (149.94)
Compression ratio8.4
Compression pressure (at 200 - 300 RPM)KPa (kg/cm 2 , psi)981 - 1,177 (10 - 12, 142 - 171)
Number of piston ringsPressure ring: 2, Oil ring: 1
Intake valve timingOpenMax. retardATDC 5°
Min. advanceBTDC 35°
CloseMax. retardABDC 65°
Min. advanceABDC 25°
Exhaust valve timingOpenBBDC 55°
CloseATDC 5°
Valve clearanceMm (in)Inspection valueIntake0.20 +004 -0.06 (0.0079 +00016 -0.0024 )
Exhaust0.35±0.05 (0.0138±0.0020)
Adjustment valueIntake0.20 +001 -0.03 (0.0079 +00004 -0.0012 )
Exhaust0.35±0.02 (0.0138±0.0008)
Idling speed (at "P" or "N" position on AT model, or neutral position on MT model)RPMNo load700±100
A/C ONAT model: 825±100
MT model: 800±100
Ignition order1 --> 3 --> 2 --> 4
Ignition timingBTDC/RPMAT model: 17°±10°/700
MT model: 12°±10°/700
Belt tension adjusterProtrusion of adjuster rodMm (in)5.2 - 6.2 (0.205 - 0.244)
CamshaftBending limitMm (in)0.020 (0.00079)
Cam lobe heightMm (in)IntakeStandard46.55 - 46.65 (1.833 - 1.837)
ExhaustStandard46.75 - 46.85 (1.841 - 1.844)
Cam base circle diameterMm (in)Standard37.0 (1.457)
Journal O.D.Mm (in)FrontStandard37.946 - 37.963 (1.4939 - 1.4946)
Center, rear29.946 - 29.963 (1.1790 - 1.1796)
Oil clearanceMm (in)Standard0.037 - 0.072 (0.0015 - 0.0028)
Thrust clearanceMm (in)Standard0.068 - 0.116 (0.0027 - 0.0047)
Cylinder headWarping limit (Mating surface with cylinder block)Mm (in)0.035 (0.0014)
Grinding limitMm (in)0.3 (0.012)
Standard heightMm (in)127.5 (5.02)
Valve seatSeating angle between valve and valve seat90°
Contacting width between valve and valve seatMm (in)IntakeStandard0.6 - 1.4 (0.024 - 0.055)
ExhaustStandard1.2 - 1.8 (0.047 - 0.071)
Valve guideClearance between the valve and valve stemMm (in)IntakeStandard0.030 - 0.057 (0.0012 - 0.0022)
Exhaust0.040 - 0.067 (0.0016 - 0.0026)
Inside diameterMm (in)6.000 - 6.012 (0.2362 - 0.2367)
Valve stem outer diametersMm (in)Intake5.955 - 5.970 (0.2344 - 0.2350)
Exhaust5.945 - 5.960 (0.2341 - 0.2346)
Valve guide protrusionMm (in)15.8 - 16.2 (0.622 - 0.638)
ValveHead edge thicknessMm (in)IntakeStandard1.0 - 1.4 (0.039 - 0.055)
ExhaustStandard1.3 - 1.7 (0.051 - 0.067)
Overall lengthMm (in)Intake104.4 (4.110)
Exhaust104.65 (4.1201)
Valve springFree lengthMm (in)47.32 (1.863)
Tension/spring heightN (kgf, lb)/mm (in)Set205 - 235 (20.9 - 24.0, 46.1 - 52.8)/36.0 (1.417)
Lift426 - 490 (43.4 - 50.0, 95.8 - 110)/26.50 (1.043)
Squareness2.5°, 2.1 mm (0.083 in) or less
Valve lifterOuter diameterMm (in)Standard34.959 - 34.975 (1.3763 - 1.3770)
Valve lifter mating surface inner diameterMm (in)Standard34.994 - 35.016 (1.3777 - 1.3786)
Valve lifter and valve lifter mating surface clearanceMm (in)Standard0.019 - 0.057 (0.0007 - 0.0022)
Cylinder blockWarping limit (Mating surface with cylinder head)Mm (in)0.025 (0.0098)
Grinding limitMm (in)0.1 (0.004)
Standard heightMm (in)201.0 (7.91)
TaperMm (in)Standard0.015 (0.0006)
Out-of-roundnessMm (in)Standard0.010 (0.0004)
Cylinder to piston clearance at 20°C (68°F)Mm (in)Standard0.010 - 0.010 (-0.00039 - 0.00039)
Cylinder inner diameter boring limit (diameter)Mm (in)To 100.005 (3.9372)
PistonPiston grade pointMm (in)38.2 (1.50)
Outer diameterMm (in)StandardA99.505 - 99.515 (3.9175 - 3.9179)
B99.495 - 99.505 (3.9171 - 3.9175)
0.25 (0.0098) OS99.745 - 99.765 (3.9270 - 3.9278)
0.50 (0.0197) OS99.995 - 100.015 (3.9368 - 3.9376)
Piston pinDegree of fitPiston pin must be fitted into position with thumb at 20°C (68°F).
Clearance between piston hole and piston pinMm (in)Standard0.004 - 0.008 (0.0002 - 0.0003)
Piston ringPiston ring gapMm (in)Top ringStandard0.20 - 0.25 (0.0079 - 0.0098)
Second ringStandard0.37 - 0.52 (0.015 - 0.0203)
Oil ringStandard0.20 - 0.50 (0.0079 - 0.0197)
Clearance between piston ring and piston ring grooveMm (in)Top ringStandard0.040 - 0.080 (0.0016 - 0.0031)
Second ringStandard0.030 - 0.070 (0.0012 - 0.0028)
Connecting rod and connecting rod bearingBend or twist per 100 mm (3.94 in) in lengthMm (in)Limit0.10 (0.0039)
Thrust clearanceMm (in)Standard0.070 - 0.330 (0.0028 - 0.0130)
Oil clearanceMm (in)Standard0.017 - 0.045 (0.0007 - 0.0018)
Bearing size (Thickness at center)Mm (in)Standard1.490 - 1.502 (0.0587 - 0.0591)
0.03 (0.0012) US1.504 - 1.512 (0.0592 - 0.0595)
0.05 (0.0020) US1.514 - 1.522 (0.0596 - 0.0599)
0.25 (0.0098) US1.614 - 1.622 (0.0635 - 0.0639)
Bushing of small endClearance between piston pin and bushingMm (in)Standard0 - 0.022 (0 - 0.0009)
Crankshaft and crankshaft bearingBending limitMm (in)0.035 (0.0014)
Crank pinOut-of-roundnessMm (in)0.003 (0.0001)
CylindricallyMm (in)0.004 (0.0002)
Grinding limit (dia.)Mm (in)To 51.750 (2.0374)
Crank journalOut-of-roundnessMm (in)0.005 (0.0002)
CylindricallyMm (in)0.006 (0.0002)
Grinding limit (dia.)Mm (in)To 59.758 (2.3527)
Crank pin outer diameterMm (in)Standard51.984 - 52.000 (2.0466 - 2.0472)
0.03 (0.0012) US51.954 - 51.970 (2.0454 - 2.0461)
0.05 (0.0020) US51.934 - 51.950 (2.0447 - 2.0453)
0.25 (0.0098) US51.734 - 51.750 (2.0368 - 2.0374)
Crank journal outer diameterMm (in)Standard59.992 - 60.008 (2.3619 - 2.3625)
0.03 (0.0012) US59.962 - 59.978 (2.3607 - 2.3613)
0.05 (0.0020) US59.942 - 59.958 (2.3599 - 2.3605)
0.25 (0.0098) US59.742 - 59.758 (2.3520 - 2.3527)
Bearing size (Thickness at center)Mm (in)#1, #3Standard1.998 - 2.011 (0.0787 - 0.0792)
0.03 (0.0012) US2.017 - 2.020 (0.0794 - 0.0795)
0.05 (0.0020) US2.027 - 2.030 (0.0798 - 0.0799)
0.25 (0.0098) US2.127 - 2.130 (0.0837 - 0.0839)
#2, #4, #5Standard2.000 - 2.013 (0.0787 - 0.0793)
0.03 (0.0012) US2.019 - 2.022 (0.0795 - 0.0796)
0.05 (0.0020) US2.029 - 2.032 (0.0799 - 0.0800)
0.25 (0.0098) US2.129 - 2.132 (0.0838 - 0.0839)
Thrust clearanceMm (in)Standard0.030 - 0.115 (0.0012 - 0.0045)
Oil clearanceMm (in)Standard0.010 - 0.030 (0.0004 - 0.0012)
NOTE: OS: Oversize US: Undersize
NOTE
OS: Oversize US: Undersize

SPECIFICATION CHART

Scheme 562

Scheme 562: TIMING BELT

Tightening torque: N.m (kgf-m, ft-lb)

T1: 3.4 (0.3, 2.5)

T2: 5 (0.5, 3.7)

T3: 6.4 (0.7, 4.7)

T4: 9.75 (1.0, 7.2)

T5: 24.5 (2.5, 18.1)

T6: 25 (2.5, 18A)

T7: 39 (4.0, 28.8)

T8: Ref. to INSTALLATION, Cam Sprocket.

T9: Ref. to INSTALLATION, Crank Pulley.

Scheme 563

Scheme 563: CYLINDER HEAD AND CAMSHAFT

Tightening torque: N.m (kgf-m, ft-lb)

T1: 6.4 (0.7, 4.7)

T2: 8 (0.8, 5.9)

T3: 29 (3.0, 21.4)

T4: Ref. to INSTALLATION, Cylinder Head.

T5: Ref. to INSTALLATION, Camshaft.

T6: Ref. to INSTALLATION, Camshaft.

T7: Ref. to INSTALLATION, Camshaft.

Scheme 564

Scheme 564: CYLINDER HEAD AND VALVE ASSEMBLY

Scheme 565

Scheme 565: CYLINDER BLOCK

Tightening torque: N.m (kgf-m, ft-lb)

T1: 5 (0.5, 3.7)

T2: 6.4 (0.7, 4.7)

T3: 10 (1.0, 7.2)

T4

First 12 (1.2, 8.9)

Second 12 (1.2, 8.9)

T5: 16 (1.6, 11.8)

T6: 25 (2.5, 18.4)

T7: 44 (4.5, 32.5)

T8: 45 (4.6, 33.2)

T9: 70 (7.1, 51.6)

T10: Ref. to INSTALLATION, Cylinder Block.

Scheme 566

Scheme 566: CRANKSHAFT AND PISTON

Tightening torque: N.m (kgf-m, ft-lb)

T1: 52 (5.3, 38.4)

T2: 72 (7.3, 53.1)

Scheme 567

Scheme 567: ENGINE MOUNTING

Tightening torque: N.m (kgf-m, ft-lb)

T1: 35 (3.6, 25.8)

T2: 85 (8.7, 62.7)

Refer to "Cylinder Head" for removal and installation procedures of the intake and exhaust valves. Ref. to REMOVAL, Cylinder Head. Ref. to INSTALLATION, Cylinder Head.

Refer to "Cylinder Block" for removal and installation procedures of pistons. Ref. to REMOVAL, Cylinder Block. Ref. to INSTALLATION, Cylinder Block.

Refer to "Cylinder Block" for removal and installation procedures of connecting rod. Ref. to REMOVAL, Cylinder Block. Ref. to INSTALLATION, Cylinder Block.

Refer to "Cylinder Block" for removal and installation procedures of the crankshaft. Ref. to REMOVAL, Cylinder Block. Ref. to INSTALLATION, Cylinder Block.