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ENGINE SPECS

1955 Plymouth 258 V8 Engine Specs

GENERAL SPECIFICATIONS

Model Designation: Eight Cylinder
     Available in Plaza, Savoy, and Belvedere Models - P27
Wheel base: 115
Valve Location: In head
Bore and Stroke: 3.5625 x 3.250
Piston displacement, Cubic Inches: 259
Compression ratio: 7.6
Maximum Brake Horsepower: 2 bbl: 167 @ 4400 RPM; 4 bbl: 177 @ 4400 RPM
Maximum Torque Lbs.Ft. @ RPM: 2bbl: 231 @ 2400; 4bbl: 231 @ 2800
Normal Oil Pressure Pounds: 50-65

TUNE UP SPECIFICATIONS

Spark Plug Make: Auto-Lite 4S-165
Spark Plug Gap, Inch: .035
Firing Order: 18436572; front to rear: left bank: 1-3-5-7, right bank 2-4-6-8
Ignition Timing: 4 degrees BTDC. Timing mark on pulley
Engine Idle Speed, RPM: In neutral: 500
Cylinder Head Torque Lbs.Ft.: 85
Compression Pressure & Cranking Speed: 125
Voltage & Polarity: 6 volts, positive ground

PISTON AND RING SPECIFICATIONS

Fitting Pistons with Scale:
Shim thickness to use: .0015
Pounds Pull On Scale: 5-10
Ring End Gap: (Fit rings in tapered bores for clearance shown in tightest portion of ring travel.)
Compression: .010
Oil: .010
Wristpin Diameter, Inch: .8592

VALVE SPECIFICATIONS

Operating Clearance:
     Intake: 0  Exhaust: 0
Valve Seat Angle, degrees: 45
Valve Timing: (BTDC = before top dead center; ATDC = after top dead center)
         Intake opens: 14 degrees BTDC
         Exhaust Closes: 9 ATDC
Valve Spring Pressure Pounds at Inches Length:
     Spring: 140 @ 1-5/16
Valve Stem Clearance:
    Intake: .001-003
    Exhaust: .002-.004
Valve Lift Zero Lash: Intake: .360 Exhaust: .360
Stem Diameter: Intake: .372-.373; Exhaust: .372-.373

ENGINE BEARING SPECIFICATIONS

Connecting Rod Bearings:
    Journal Diameter, Inches: 1.9375
    Bearing Clearance, Inch: .0005-.0015
Main Bearings:
    Journal Diameter, Inches: 2.374-2.375
    Bearing clearance: .0005-.0015
    Shaft End Play: .002-.007   (Thrust on Bearing No. 3)

CAPACITY DATA

Cooling System:
    Without heater: 19 quarts
    With heater: 20 quarts
    Radiator Cap Relief Pressure: 7, 14 lbs with air conditioning
    Thermostat Opening Temp.: 180

Fuel Tank: 17 gallons
Engine Oil: 5 quarts; add 1 quart for filter change
Transmission: standard: 2-3/4 pints; w/overdrive: 3-1/2; Automatic: 10
Rear Axle: 3-1/4 pints

DISTRIBUTOR SPECIFICATIONS

Distributor part number: 1AZ-4003C, 1AZ-4003E, 1AZ-4003G, 1AZ-4003H (distributor rotates clockwise)
Cam Angle, degrees: Each set 26-28; total dwell both sets 32-36
Breaker Point opening, Inch: .017
Condenser Capacity: .25-.28 Mfds.
Breaker Arm Spring Tension: 17-20 Oz.
Centrifugal Advance: (degrees at RPM of distributor)
    1AZ-4003 C & E:
    
   Advance starts 1 degrees @ 375
       Full Advance: 18 degrees @ 1900
    1AZ-4003 G & H:

        Advance starts 1 degrees @ 375
        Full Advance: 16 degrees @ 1650

Vacuum Advance Data:
    1AZ-4003C:
         Inches of vacuum to start plunger movement: 5-1/4
        Inches of vacuum for full plunger travel: 17
        Maximum vacuum advance, Dist. degrees: 11-1/2
    1AZ-4003E:
        Inches of vacuum to start plunger movement: 5-1/4
        Inches of vacuum for full plunger travel: 11-1/4
        Maximum vacuum advance, Dist. degrees: 7
    1AZ-4003G:
        Inches of vacuum to start plunger movement: 5-1/4
        Inches of vacuum for full plunger travel: 8-1/2
        Maximum vacuum advance, Dist. degrees: 4
    1AZ-4003H:
        Inches of vacuum to start plunger movement: 5-1/4
        Inches of vacuum for full plunger travel: 17
        Maximum vacuum advance, Dist. degrees: 11-1/2

GENERATOR SPECIFICATIONS

Generator Number: GGW-6012B, GGW-6016A (generator rotates clockwise, 6 volts, Positive Ground)
Generator output: 45 @ 2125 RPM
Brush Spring Tension: 35-53 oz.
Field Current: 1.4 - 1.5 at 5 volts

REGULATOR SPECIFICATIONS

Regulator Number: VBE-6201A
Cutout Relay:
    Voltage to close points: 6.5
    Armature Air Gap: .032
Voltage Regulator Setting: 7.2 volts
Current Regulator Setting: 45 amps
Current and voltage armature air gap, Inch: .050

STARTING MOTOR SPECIFICATIONS

Part number: MCH-6206 (starter rotates clockwise)
Bush Spring Tension, Ounces: 42-53
No Load Test: 65 amps, 5.0 volts @ 4300 RPM
Torque Test: 335 Amps, 2.0 volts, Torque, Lbs.Ft.: 6

ENGINE TIGHTENING SPECIFICATIONS (FT. LBS.)

Spark Plugs: 30
Cylinder Head Bolts: 85
Intake Manifold: 30
Exhaust Manifold: 25
Rocker Arm Shaft Bracket: 30
Rocker Arm Cover: 20-25 inch/lbs.
Connecting Rod Cap Bolts: 45
Main Bearing Cap Bolts: 85
Flywheel to Crankshaft: 60
Vibration Damper or Pulley: 135

REAR AXLE AND BRAKE CYLINDER SPECIFICATIONS

Ring Gear & Pinion Backlash, Inch: .006-.010
Drive Pinion Adjustment: Shims
Drive Pinion Bearing Adjustment: Washer
Hydraulic Cylinder Bore Sizes, Inch:
    Wheel Cylinder:
        Front:
1-1/8
        Rear: 1-1/8
    Master Cylinder: 1-1/8

WHEEL ALIGNMENT SPECIFICATIONS

Caster, Degrees
    Limits: -2 to 0
    Desired: -1
Camber, Degrees
    Limits: -1/8 to +5/8
    Desired: 1/2 on left side and 0 on right side
Toe-In, Inches: 1/8
Toe-Out on Turns, Degrees: (If toe-out is incorrect, when other adjustments are correct, look for bent steering arms.)
    Outer wheel: 20
    Inner Wheel: 20-1/2 to 22-1/2
Kingpin Angle, or Steering Axis Degrees: (If king pin or spindle support angle are incorrect, but camber is correct, look for bent suspension arms or steering knuckle support)
    5 to 6-1/2

·  Understanding Second Chance Garage's Vintage Auto Engine Specs





 

 

 

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