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Engine Mechanical (H4SO) (Except Sti): Specifications Subaru Impreza GH

Mechanical 7 illustrations ~286 words

SPECIFICATION

EngineModel2.5 L
Cylinder arrangementHorizontally opposed, liquid cooled, 4-cylinder, 4-stroke gasoline engine
Valve system mechanismBelt driven, single overhead camshaft, 4 valve/cylinder
Bore x StrokeMm (in)99.5x79.0 (3.92x3.11)
DisplacementCm 3 (cu in)2,457 (149.94)
Compression ratio10.0
Compression pressure 2 (at 200 - 300 RPM)KPa (kg/cm 2 , psi)1,020 - 1,275 (10.4 - 13.0,148 - 185)
Number of piston ringsPressure ring: 2, Oil ring: 1
Intake valve timingConstantOpenBTDC 0°
CloseABDC 58°
Low speedOpenBTDC 0°
CloseABDC-10°
High speedOpenBTDC 14°
CloseABDC 62°
Exhaust valve timingOpenBBDC30°
CloseATDC14°
Valve clearanceMm (in)Intake0.20±0.04 (0.007910.0016)
Exhaust0.25±0.04 (0.0098±0.0016)
Idling speed (at "P" or "N" position on AT model, or neutral position on MT model)RPMNo loadAT model: 700±100
MT model: 650±100
A/CON85±100
Ignition order1-->3-->2-->4
Ignition limingBTDC/RPMAT model: 15°±10°/700
MT model: 10°±8°/650

GENERAL SPECIFICATION

Note. US: Undersize OS: Oversize

Belt tension adjusterProtrusion of adjuster rodMm (in)5.2 - 6.2 (0.205 - 0.244)
Valve rocker armClearance between shaft and armMm (in)Standard0.020 - 0.054 (0.0008 - 0.0021)
CamshaftBending limitMm (in)0.025 (0.00098)
Cam lobe heightMm (in)IntakeConstantStandard40.075 - 40.175 (1.5778 - 1.5817)
Low speedStandard35.496 - 35.596 (1.3975 - 1.4014)
High speedStandard40.315 - 40.415 (1.5872 - 1.5911)
ExhaustStandard39.289 - 39.389 (1.5468 - 1.5507)
Cam base circle diameterMm (in)Standard34.00 (1.3386)
Base circle step of adjacent intake cams (low speed and high speed)Mm (in)Standard0.03 (0.001)
Journal O.D.Mm (in)31.928 - 31.945 (1.2570 - 1.2577)
Cylinder head journal I.D.Mm (in)32.000 - 32.018 (1.2598 - 1.2605)
Thrust clearanceMm (in)Standard0.030 - 0.090 (0.0012 - 0.0035)
Oil clearanceMm (in)Standard0.055 - 0.090 (0.0022 - 0.0035)
Cylinder headWarping limit (Mating surface with cylinder block)Mm (in)0.035 (0.0014)
Grinding limitMm (in)0.1 (0.004)
Standard heightMm (in)97.5 (3.84)
Valve seatSeating angle between valve and valve seat90°
Contacting width between valve and valve seatMm (in)StandardIntake0.8 - 1.4 (0.03 - 0.055)
Exhaust1.2 - 1.8 (0.047 - 0.071)
Valve guideClearance between the valve guide and valve stemMm (in)StandardIntake0.035 - 0.062 (0.0014 - 0.0024)
Exhaust0.040 - 0.067 (0.0016 - 0.0026)
Inside diameterMm (in)6.000 - 6.012 (0.2362 - 0.2367)
Valve stem outer diametersMm (in)Intake5.950 - 5.965 (0.2343 - 0.2348)
Exhaust5.945 - 5.960 (0.2341 - 0.2346)
Valve guide protrusionMm (in)Intake20.0 - 21.0 (0.787 - 0.827)
Exhaust16.5 - 17.5 (0.650 - 0.689)
ValveHead edge thicknessMm (in)StandardIntake0.8 - 1.2 (0.03 - 0.047)
Exhaust1.0 - 1.4 (0.039 - 0.055)
Overall lengthMm (in)Intake120.6 (4.75)
Exhaust121.7 (4.79)
Valve springFree lengthMm (in)55.2 (2.173)
Tension/spring heightN (kgf, lb)/mm (in)Set235.3 - 270.7 (24 - 27.6, 52.9 - 60.8)/45.0 (1.772)
Lift578.9 - 639.9 (59.1 - 65.3,130.3 - 143.9)/34.7 (1.366)
Squareness2.5°, 2.4 mm (0.094 in) or less
Cylinder blockWarping limit (Mating surface with cylinder head)Mm (in)0.025 (0.00098)
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 (1.504)
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 - 3.9277)
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 - 0.35 (0.0079 - 0.0138)
Second ringStandard0.37 - 0.52 (0.0146 - 0.0205)
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)Standard0.016 - 0.044 (0.0006 - 0.0017)
Bearing size (Thickness at center)Mm (in)Standard1.492 - 1.501 (0.0587 - 0.0591)
0.03 (0.0012) US1.510 - 1.513 (0.0594 - 0.0596)
0.05 (0.0020) US1.520 - 1.523 (0.0598 - 0.0600)
0.25 (0.0098) US1.620 - 1.623 (0.0638 - 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)
CylindricalityMm (in)0.004 (0.0002)
Grinding limit (dia.)Mm (in)To 51.750 (2.0374)
Crank journalOut-of-roundnessMm (in)0.005 (0.0002)
CylindricalityMm (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 (2.0446 - 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)

GENERAL SPECIFICATION

Scheme 341

Scheme 341: TIMING BELT

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

T1. 5 (0.5,3.7)

T2: 9.75 (1.0,7.2)

T3: 24.5 (2.5,18.1)

T4: 39 (4.0,28.8)

T5: 78 (8.0,57.5)

T6: Refer to INSTALLATION , Crank Pulley.

Scheme 342

Scheme 342: CYLINDER HEAD AND CAMSHAFT

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

T1. 6 (0.6,4A)

T2: 6.4 (0.7,4.7)

T3: 8 (0.8,5.9)

T4: 9.75 (1.0,7J2)

T5: 10 (1.0,7.4)

T6: 17 (1.7, 12.5)

T7: 18 (1.8,13.3)

T8: 25 (2.5,18.4)

T9: Refer to INSTALLATION , Cylinder Head.

T10: Refer to INSTALLATION , Valve Rocker Assembly.

Scheme 343

Scheme 343: VALVE ROCKER ASSEMBLY

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

T1: 6 (0.6,4.4)

T2: 9.75 (1.0,7.2)

T3: 25 (2.5,18.4)

Scheme 344

Scheme 344: CYLINDER HEAD AND VALVE ASSEMBLY

Scheme 345

Scheme 345: 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 (1.0,7.4)

T4: 25 (2.5, 18.4)

T5: Refer to INSTALLATION , Cylinder Block.

T6: 16 (1.6,11.8)

T7: First 12 (1,2,8.7) Second 12 (1.2, 8.7)

T8: 44 (4.5,32.5)

T9: 45 (4.6,33.2)

T10: 70 (7.1,51.6)

Scheme 346

Scheme 346: CRANKSHAFT AND PISTON

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

T1: 45 (4.6,33.2)

T2: 72 (7.3,53.1)

Scheme 347

Scheme 347: ENGINE MOUNTING

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

T1: 35 (3.6,25.8)

T2: 42 (4.3,31.0)

T3: 85 (8.7,62.7)

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

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

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

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