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401

General Specifications for the 1966 Buick 401 and 425 Cubic Inch Engines The following information has been directly complied from original Buick service manuals for the respective year of vehicle manufacture. These specifications should also be correct for the 1966 model year.


BOLT TORQUE SPECIFICATIONS

Use a reliable torque wrench to obtain the figures listed below. This will prevent straining or distorting the parts as well as preventing thread damage. These specifications are for clean and lightly lubricated threads only. Dry or dirty threads produce friction which prevents accurate measurement of the actual torque. It is important that these specifications be strictly observed. Overtightening can damage threads. This will prevent attainment 'of the proper torque and will require replacement of the damaged part.

AreaLb. Ft.
Spark Plugs25-35
Crankshaft Bearing Caps to Cylinder Block80-110
Connecting Rods40-50
Cylinder Head to Cylinder Block65-80
Harmonic Balancer to Crankshaft200 Minimum
Fan Driving Pulley to Harmonic Balancer18-25
Flywheel .to Crankshaft (Auto. & Manual)50-65
Oil Pan to Cylinder Block9-13
Oil Pan Drain Plug25-35
Oil Pump Cover to Oil Pump8-12
Oil Pick-Up Tube & Screen Housing Assembly to Oil Pump6-9
Oil Pump to Cylinder Block30-40
Oil Gallery Plugs25-35
Oil Filter to Cylinder Block10-15
Timing Chain Cover to Block17-23
Water Pump Cover to Timing Chain Cover6-8
Fan Driven Pulley17-23
Thermostat Housing to Intake Manifold17-23
Intake Manifold to Cylinder Head25-35
Exhaust Manifold to Cylinder Head10-15
Carburetor to Intake Manifold10-15
Fuel Pump to Cylinder Block25-40
Motor Mount to Cylinder Block25-40
Fuel Pump Eccentric and Timing Chain Sprocket to Camshaft40-55
Rocker Arm Cover to Cylinder Head3-5
Rocker Arm Shaft Bracket to Cylinder Head25-35
Delcotron Bracket to Cylinder Head65-80
Delcotron Bracket Brace18-25
Delcotron Adjustable Mounting Bracket to Cylinder Head25-40
Delcotron Mounting Bracket Thru Delcotron to Cylinder Head at Pivot Location35-45
Starting Motor to Block40-55
Distributor Hold-Down Clamp10-15
Synchromesh Lower Flywheel Housing Plate9-13
Flywheel Housing to Cylinder Block45-60
Fuel Filter to Cylinder Head7-10
401

GENERAL SPECIFICATIONS

General
 Wildcat 445
(400 & 401 Co. In.)		Wildcat 465
(425 Cu. In.)
Code Number PrefixMR (400), MT (401)MW
Export Code Number PrefixMVNot Available
Engine Type90° V-890° V-8
Bore and Stroke4.1875 x 3.6404.3125 x 3.640
Piston Displacement400 & 401 Cu. In.425 Cu. In.
Carburetor Type 4 Bbl.4 Bbl.
Compression Ratio10.25:110.25:1
Gasoline RequirementsPremiumPremium
Brake Horsepower @ RPM325/4400340/4400
Maximum Torque § RPM445/2800465/2800
Taxable Horsepower56.1159.51
Octane Requirements - Motor9090
Octane Requirements - Research9999
Cylinder Numbers - Front to Rear - Left Bank2-4-6-82-4-6-8
Cylinder Numbers - Front to Rear - Right Bank1-3-5-71-3-5-7
Firing Order1-2-7-8-4-5-6-31-2-7-8-4-5-6-3

Piston and Pin Specifications
Piston MaterialCast Aluminum Alloy
TypeDivorced Skirt
FinishCam Ground
Piston Pins 
     MaterialExtruded SAE-1018
     TypePressed in Rod

Connecting Rods
MaterialForged - SAE-1141 Steel
Rod BearingRemovable Steel Backed M/400

Ring Specifications
#1 CompressionCast Iron-Lubrited
#2 CompressionCast Iron-Lubrited
Oil ControlSteel-Uncoated
Oil Ring ExpanderSteel Humped Ring
Ring LocationsAbove Pin

Crankshaft Specifications
MaterialSAE-1145 or SAE-1053 Steel
Bearings5 Replaceable Steel Backed
Bearing Material#1, #2, #3, and #4 - M/400, #5 - 100A Durex
Bearing Taking End Thrust#3

Camshaft Specifications
MaterialCast Alloy Iron
BearingsSteel Backed Bobbitt
Number of Bearings5
DriveChain
Number of Links52
Crankshaft SprocketSintered Iron
Camshaft SprocketNylon Coated Aluminum

Valve Specifications
Intake Valve MaterialSAE 1041 Steel, 1047 or TS 8150 Steel
Exhaust Valve MaterialGM-N82152 (21 - 4N)
Valve Lifter MechanismHydraulic
Valve SpringSingle Helical

Lubrication System Specifications
Type of Lubrication  
     Main BearingsPressure
     Connecting RodsPressure
     Piston PinsSplash
     Camshaft BearingPressure
     Timing ChainDrip from Front Cam Bearing
     Cylinder WallsSplash & Nozzle
Oil Pump TypeGear Driven
Normal Oil Pressure40 Ibs. @ 2400 RPM
Oil Pressure Sending UnitElectrical
Oil IntakeStationary
Oil Filter SystemFull Flow
Filler TypeThrow-Away Element & Can
Crankcase Capacity  
     Less Filter4 qts.
     With Filter5 qts.

Cooling System Specifications
System TypePressure
Radiator Cap Relief Pressure15 psi
ThermostatChoke Type Opening at 180°
Water Pump TypeCentrifugal
     GPM @ RPM17 @ 1000
     DriveV-Belt
     BearingsDouble Row
By-Pass Recirculation TypeInternal
Cooling System Capacities 
With Heater18.0 qts.
W/O Heater17.0 qts.
With Air Conditioning18.27 qts.
Fan Diameter and Number of Blades 
     Less AC18" x 4
     With AC20" x 5
Fan Drive 
     Less ACWater Pump Shaft
     With ACThermostatic Controlled Clutch

Engine Dimentions and Fits
Piston Clearance Limits*
 400 &
401 Cu. In.		425 Cu. In.
Top Land.034 - .042.034 - .042
Skirt - Top.0004 - .0010.0004 - .0010
Skirt - Bottom.0019 - .0035 .0019 - .0035
Ring Groove
     #1 - Compression Ring.211 - .219.209 - .217
     #2 - Compression Ring.214 - .221.212 - .219
     #3 - Oil Ring.214 - .221.192 - .199
Ring Width
     #1 - Compression Ring.077 - .078.077 - .078
     #2 - Compression Ring.077 - .078.077 - .078
     #3 - Oil Ring.181 - .187.182 - .1885
Ring Gap
     #1 - Compression Ring.015 - .025.015 - .025
     #2 - Compression Ring.015 - .025.015 - .025
     #3 - Oil Ring.015 - .055.015 - .055
Piston Pin Length3.5203.520
Diameter of Pin.9994 - .9997.9994 - .9997
Clearance
     In Piston.0001 - .0004.0001 - .0004
     In Rod.00075 .00125 Press
Direction & Amount Offset in PistonNoneNone
*A11 Measurements in Inches Unless Otherwise Specified.

Connecting Rod Specifications
Bearing Length.820
Bearing Clearance (Limits).0020 - .0023
End Play-Total for Both Rods.005 - .012

Crankshaft Specifications
End Play at Thrust Bearing.004 - .008
Main Bearing Journal Diameter2.4985
Crankpin Journal Diameter2.2495
Main Bearing Overall Length
     #1.940
     #2.940
     #31.127
     #4.940
     #51.200
Main Bearing to Journal Clearance.000 - .0019
Bearing Journal Diameter
     #11.785 - 1.786
     #21.755 - 1.756
     #31.725 - 1.726
     #41.695 - 1.696
     #51.665 - 1.666

Valve System Specifications
Rocker Arm Ratio1.6 to 1
Rocker Arm Clearance on Shaft.0027 - .0042
Valve Lifter Diameter.8425
Valve Lifter Clearance in Crankcase.0015 - .0030
Valve Lifter Leakdown Rate12 to 60 Sec. in Test Fixture
Intake Valve
     Head Diameter1.875
     Seat Angle45°
     Stem Diameter(Top) 3.73 (Bottom) .372
     Clearance in Guide(Top) .001 - .003 (Bottom) .002 - .004
     Valve Spring (Inner)
     Valve Closed - Pounds @ Length25.2 @ 1.690
     Valve Open - Pounds § Length76 @ 1.250
Valve Spring (Outer)
     Valve Closed - Pounds § Length46 @ 1.600
     Valve Open - Pounds § Length101 @ 1.160
Exhaust Valve
     Head Diameter1.500
     Seat Angle45°
     Stem Diameter(Top) .372 (Bottom) .3715
     Clearance in Guide(Top) .0015 - .0035 (Bottom) .0025 - .0045
Valve Spring (Inner)
     Valve Closed - Pounds § Length25.5 @ 1.690
     Valve Open - Pounds @ Length76 @ 1.250
Valve Spring (Outer)
     Valve Closed - Pounds @ Length46 @ 1.600
     Valve Open - Pounds @ Length101 @ 1.160

 
 
 


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