Original British Leyland Press Release for the MGB GT V8

STUDENTS TECHNICAL NOTES

PRODUCT TRAINING DEPARTMENT



Austin Morris Group
British Leyland UK Limited
Service and KD Division
Cowley, Oxford OX4 2PG England


SUBJECT MGBGTV8

MGB GT V8 ENGINE

GENERAL DESCRIPTION

The cylinder block is cast aluminum fitted with cylinder liners. It has two banks of four cylinders each, which form a 90 degree angle.

The crankshaft is supported by five bearings. The thrust is taken by the centre main bearing. Connecting rods are forged steel, and aluminum alloy pistons are used. These are fitted with two compression and one oil control ring above the gudgeon pin which is semi-floating (press fit).

Cylinder heads are also aluminum castings. Iron valve seat inserts and valve guides are used. The valves are arranged in line and operate at an angle of 10 degrees above the cylinder bore center line. The camshaft is located between the two banks of cylinders, above the crankshaft, and runs in five bearings. It is driven at half the crankshaft speed by an inverted tooth type chain. No chain tensioner is provided.

The valves are operated by means of hydraulic tappets which ensure quiet engine running and maintain adjustment at the correct clearance.

Lubrication of the engine is by means of a pressure fed oil system, which incorporates an oil pump located in the timing cover, and an external full flow oil filter.

Product Training (Cars)
June 1973


 Please support the sponsoring companies who make British V8 possible, including:

TECHNICAL DATA

8 degrees BTDC at 1000 rev/min
ENGINE
Unit typeV8
No. of cylindersEight, two banks of four
Capacity215.54 in.3 (3 532 cm3)
Bore3.50 in. (88,9 mm)
Stroke2.80 in. (71,12 mm)
Firing order1 - 8 - 4 - 3 - 6 - 5 - 7 - 2
Cylinder numbering - left bank1 - 3 - 5 - 7 (front to rear)
Cylinder numbering - right bank2 - 4 - 6 - 8 (front to rear)
Cranking pressure155 lbf/in2 (109 kgf/cm2) at 200 rev/min
Compression ratio8.26 : 1
Torque193.0 lbf/in (26,33 kgf m) at 2,900 rev/min
Engine idle speed800 to 850 rev/min
Fast idle speed1 400 to 1 500 rev/min
Valve operationOverhead by push rod
B.H.P.137 at 5000 rev/min din
     
FUEL
Recommended octane rating97 RON (Research octane number) minimum
     
CRANKSHAFT
Main journal dia.2.2992 to 2.2997 in. (58,40 to 58,41 mm)
Crankpin journal dia.2.000 to 2.0005 in. (50,80 to 50,81 mm)
Undersizes (mains and crankpin)0.100 in. 0.020 in. 0.030 in. 0.040 in.
(0,25 mm) (0,51 mm) (0,76 mm) (1,02 mm)
Crankshaft end floatTaken on No. 3 main bearing
Crankshaft Regrind0.004 to 0.008 in. (0,10 to 0,20 mm)
     
MAIN BEARING
Number and type5 thin wall
Length - Nos. 1,2,4 & 50.791 to 0.807 in. (20,12 to 20,50 mm)
Length - No. 31.056 to 1.058 (26,82 to 26,87 mm)
Diametrical clearance0.0004 to 0.0021 in. (0,01 to 0,05 mm)
     
CON RODS
TypeHorizontally split big end, plain small end.
Length between centres5.658 to 5.662 in. (143,71 to 143,81 mm)
End float on crankpin0.006 to 0.014 in. (0,15 to 0,36 mm)
Small end dia.0.8734 to 0.8739 in. (22,184 to 22,187 mm)
     
BIG END BEARING
TypeThin wall
Length0.687 to 0.702 in. (17,45 to 17,83 mm)
Diametrical clearance0.0006 to 0.0023 in. (0,02 to 0,06 mm)
     
GUDGEON PIN
TypePress fit in connecting rod
Dia. (outer)0.8745 to 0.8748 in. (22,21 to 22,22 mm)
Fit to piston0.0002 to 0.0004 in. (0,005 to 0,010 mm)
Fit in con. rodInterference
Gudgeon Pin Torque12 lbs/ft
     
PISTONS
TypeAluminum alloy, concave top
Clearance - top of skirt0.0019 to 0.0025 in. (0,05 to 0,06 mm)
Clearance - bottom of skirt0.0007 to 0.0013 in. (0,02 to 0,03 mm)
Oversizes available0.010 in. (0,25 mm) 0.020 in. (0,51 mm)
Width of groove - top0.081 to 0.082 in. (2,06 to 2,08 mm)
Width of groove - second0.081 to 0.082 in. (2,06 to 2,08 mm)
Width of groove - third0.1885 to 0.1895 in. (4.79 to 4.81 mm)
Gudgeon pin bore0.8748 to 0.8751 in. (22,22 to 22,23 mm)
Piston gradingA - 0.0003"-0006"
 B - 0.0006"-0009"
 C - 0.0009"-0012"
 D - 0.0023"-0015"
     
PISTON RINGS
Compression2
Top ringTapered, chrome faced
Second ringTapered
Fitted gap0.017 to 0.022 in. (0,43 to 0,56 mm)
Groove clearance - top0.002 to 0.0035 in. (0,05 to 0,09 mm)
Groove clearance -second0.002 to 0.003 in. (0,05 to 0,08 mm)
Oil control1
TypeTwo chrome faced rings with spacer
Fitted gap - rings0.015 to 0.055 in. (0,38 to 1,40 mm)
Fitted gap -spacer0.521 to 0.589 in. (13,24 to 14,95 mm)
     
CAMSHAFT
Valve timing marksDimples on crankshaft and camshaft sprockets
AdjustmentNon adjustable
Valve timing markValve 0.004 in. (0,10 mm) off seat at timing point.
Inlet opens30 degrees BTDC
Inlet closes75 degrees ABDC
Exhaust opens68 degrees BBDC
Exhaust closes37 degrees ATDC
Bearings5 - thin wall
Journal dia. front1.785 to 1.786 (45,34 to 45,36 mm)
Journal dia. second1.755 to 1.756 (44,58 to 44,60 mm)
Journal dia. third1.725 to 1.726 (43,82 to 43,84 mm)
Journal dia. fourth1.695 to 1.696 (43,06 to 43,08 mm)
Journal dia. fifth1.665 to 1.666 (42,29 to 42,32 mm)
Diametrical clearance - front0.0005 to 0.0025 (0,01 to 0,06 mm)
Diametrical clearance - rest0.0005 to 0.0035 (0,01 to 0,09 mm)
     
TIMING CHAIN
TypeInverted tooth
Pitch and number of pitches0.375 in. (9,52 mm) pitch x 54
Controlled byChain design
     
TAPPETS
TypeHydraulic, non adjustable (not serviceable)
Diametrical Clearance0.0008 to 0.0023 in. (0,02 to 0,06 mm)
     
CYLINDER HEAD
Valve seat angle46 degrees + one quarter degree
     
VALVES
Inlet: Face angle45 degrees + one quarter degree
Inlet: Head diameter1.495 to 1.505 in. (37,97 to 38,23 mm)
Inlet: Stem diameter from head...0.3402 to 0.3412 in. (8,64 to 8,67 mm)
...increasing to0.3407 to 0.3417 in. (8,65 to 8,68 mm)
Inlet: Stem to guide clearance, top0.001 to 0.003 (0,03 to 0,08 mm)
Inlet: Stem to guide clearance, bottom0.0005 to 0.0025 in. (0,01 to 0.06 mm)
Lift0.39 in. (10,0 mm)
Exhaust: Face angle45 degrees + one quarter degree
Exhaust: Head diameter1.3075 to 1.3175 in. (33,21 to 33,47 mm)
Exhaust: Stem diameter from head...0.3397 to 0.3407 in. (8,63 to 8,65 mm)
...increasing to0.3402 to 0.3412 in. (8,64 to 8,67 mm)
Exhaust: Stem to guide clearance, top0.0015 to 0.0035 in. (0,04 to 0,09 mm)
Exhaust: Stem to guide clearance, bottom0.002 to 0.004 in. (0,05 to 0,10 mm)
Lift0.39 in. (10,0 mm)
     
VALVE ROCKERS
Shaft diameter0.8092 to 0.8099 in. (20,55 to 22,57 mm)
Arm bore diameter0.812 to 0.813 in. (20,62 to 20,65 mm)
Ratio1.56 : 1
     
VALVE GUIDES
Length2.600 in. (66,04 mm)
Outer diameter0.5942 to 0.5952 in. (15,09 to 15,12 mm)
Inner diameter0.3427 to 0.3437 in. (8,70 to 8,73 mm)
Fitted height0.745 in. (18.92mm)
Interference fit in head0.0015 to 0,0035 in. (0,04 to 0,09 mm)
     
VALVE SPRINGS
Free length, inner1.919 in. (48,74mm)
Free length, outer2.068 in. (52,53 mm)
Fitted length, inner1.630 in. (41,40 mm)
Fitted length, outer1.600 in. (40,64 mm)
Load to compress...
...to fitted length, inner24 +/- 2.5 lbf (10 +/- 1,14 kgf)
...to fitted length, outer42 +/- 3 lbf (19,1 +/- 1,36 kgf)
     
ENGINE LUBRICATION
System typeWet sump, pressure fed.
System pressure, running42 lbf/in2 (2,95 kgf/cm2)
System pressure, idling34 lbf/in2 (2,39 kgf/cm2)
     
OIL PUMP
TypeGear
     
OIL FILTER
TypeFull flow
By-pass valve opens8 to 12 lbf/in2 (0,56 to 0,84 kgf/cm2)
     
PRESSURE RELIEF VALVE
Free length3.20 in. (81,30 mm)
Fitted length1.80 in. (45,70 mm)
Load at fitted length9.3 +/- 0.5 lbf (4,22 +/- 0,23 kgf)
     
CAPACITY ENGINE
Including filter8 Imp pints - 4,54 litres
Filter1/2 pint - 0,28 litres
     
COOLING SYSTEM
TypePressurized spill return system with thermostat control, pump and fan assisted.
PumpCentrifugal
ThermostatWax element
Thermostat temperature82 degrees C
Pressure cap15 lbf/in2 (1,05 kgf/m2)
Capacity with heater16 pints (9,1 litres)
FanTwin electric
Anti-freezeBluecol type AA
Thermostatic fan cut-in88 degrees
Thermostatic fan cut-out92 degrees
     
FUEL SYSTEM
Tank capacity12 gallons
CarburettorS.U. HIF6
Damper0.070 in.
Jet size0.100 in. (2,54 mm)
NeedleBBU
Piston springYellow
Air cleanersPaper element type with air temperature control
Fuel pumpS.U. electric AUF 305
     
IGNITION DETAILS
Timing marksPointer on timing case and degree marks on crankshaft pulley.
     
Distributor
Make/typeLucas 35 D8
Serial number41394
Rotation of rotorAnti-clockwise
Dwell angle26 to 28 degrees
Contact breaker gap0.014 to 0.016 in. (0,35 to 0,40 mm)
Condensor capacity0.18 to 0.24 microfarad
Centrifugal advance (decelerating with vacuum pipe disconnected)
33 to 37 degrees at 4900 rev/min
28 to 32 degrees at 3600 rev/min
24 to 28 degrees at 2600 rev/min
19 to 23 degrees at 2000 rev/min
14 to 18 degrees at 1600 rev/min
9 to 13 degrees at 1200 rev/min
No advance below600 rev/min
Vacuum advance16 degrees
Vacuum advance - starts5 in. (127 mm) Hg.
Vacuum advance - finishes17 in. (432 mm) Hg.
Stroboscopic timing
     
Spark Plugs
Make/typeChampion L92Y
Gap0.035 in. (0,90 mm)
     
Coil
Make/typeLucas 16C6 with ballast resistor
Primary resistance at 20C (68F)1.2 to 1.4 ohms
Consumption - ignition on at 2000rpm1 amp
     
CLUTCH
TypeBorg & Beck, 9.5 in. (DS.45 SF)
Diaphragm spring colourRed on two fingers
Number of damper springs6
Damper spring colourBrown/cream
Clutch releaseBall bearing
Master cylinder diameter0.70 in. (17,78 mm)
Slave cylinder diameter1.0 in. (25,40 mm)
FluidUnipart 550
     
GEARBOX AND OVERDRIVE
Forward gearsFour (all synchromesh)
RatiosGearboxOverall
Reverse2.819 : 18.657 : 1
First3.138 : 19.637 : 1
Second1.974 : 16.062 : 1
Third1.259 : 13.866 : 1
Fourth1.000 : 13.071 : 1
Overdrive0.82 : 12.518 : 1
Road speed in top gear - direct23 m.p.h. (per 1000 rev/min)
Road speed in top gear - overdrive28 m.p.h. (per 1000 rev/min)
Speedometer gear ratio8/21
Overdrive typeLaycock LH
     
PROPELLER SHAFT
TypeTubular with Hardy Spicer joints
     
FINAL DRIVE
TypeHypoid, semi floating
Ratio3.071 : 1 (14/43)
Differential bearing preload0.002 in. (0,05 mm) "nip" per bearing
Backlash adjustment - crown wheelSpacers
Backlash adjustment - pinionHead washer
     
STEERING
TypeRack and pinion
Steering wheel diameter15.5 in. (394 mm)
Turns - lock to lock2.93
Turning circle: left lock34 ft. (10,36 m)
Turning circle: right lock33 ft. 1 in. (10,08 m)
Pinion end float0.002 to 0.005 in. (0,05 to 0,12 mm)
Damper end float0.0005 to 0.003 in. (0,01 to 0,08 mm)
Toe-in1/16 to 3.32 in. (1,6 to 2,4 mm)
     
FRONT SUSPENSION
TypeIndependent. Coil spring and wishbone.
Spring - coil diameter (mean)3.238 in. (82,2 mm)
Spring - free height9.32 +/- 0.06 in. (236,7 +/- 1,5 mm)
Spring - static length6.84 in. (173,7 mm) at 1193 lbf (540.1 kgf)
Spring - number of free coils7.2
Camber angleNominal 1 degree positive (+ 0.5 degrees, - 1.5 degrees)
Caster angleNominal 7 degrees (+ 0.25 degrees, - 2 degrees)
King pin inclinationNominal 8 degrees (+ 1 degree, - 0.75 degrees)
DampersArmstrong, lever arm, hydraulic
Damper arm centres8 in. (203,2 mm)
     
REAR SUSPENSION
TypeSemi-elliptic leaf spring
Number of spring leaves6 plus bottom plate,
Interleaving 1/2, 2/3, 3/4, 4/5.
Width of springs1.75 in. (44,4 mm)
Gauge of leaves3 at 7/32 in. (5,6 mm), 3 at 3/16 in. (4,8 mm)
Working load550 lb (249,7 kg)
DampersArmstrong, lever arm, hydraulic
Damper arm centres5.25 in. (133 mm)
     
BRAKES
TypeLockheed hydraulic, disc front, drum rear, servo assisted.
Master cylinder diameter0.75 in. (19,05 mm)
Servo typeRemote type 6
Front - caliper piston diameter2.125 in. (53,98 mm)
Front - pad area (total)24 in2 (3,72 cm2)
Front - disc diameter10,70 in. (271,78 mm)
Front - pad materialF2241 (Unipart GBP 212)
Rear - wheel cylinder diameter0.80 in. (20,32 mm)
Rear - lining area (total)67.2 in2 (10,42 cm2)
Rear - drum diameter10.0 in. (254 in.)
Rear - surface width1.75 in. (44,45 mm)
Rear - lining materialGBS 602 Lining material MA1
     
WHEELS
Size5J x 14
     
TYRES
Size and type175 HR - 14, tubeless, radial
     
ELECTRICAL EQUIPMENT
System12 volt, negative earth
Batteries (two six volt)CA 11/9E or CAZ11/9E
Capacity : 10 hour rate53 Ah
Capacity : 20 hour rate60 Ah
Plates per cell9
Electrolyte to fill one cell1 pint (570 cm3, 1.2 U.S. pints)
Fuses35A (blow rating)
     
Alternator
TypeA.C. Delco 7982707
Output at 14.2V and 5000 rev/min46A
Brush length (minimum)0.25 in. (6,3 mm)
Brush spring tension8 to 13 ozf (227 to 369 gf)
     
Starter Motor
Make and typeLucas 3M100 Pre-engaged
     
Wiper Motor
Make and typeLucas, two speed
     
Horns
Make and typeLucas 9H
Maximum current consumption3.5 to 4 amp
     
GENERAL DIMENSION
Overall width4 ft 11 15/16 in. (152,3 cm)
Overall height4 ft 1 31/32 in. (126,9 cm)
Track - front4 ft 1 in. (124.4 cm)
Track - rear4 ft 1.25 in. (125 cm)
Wheelbase7 ft 7.135 in. (231,5 cm)
Ground clearance (unladen)4.25 in. (108 mm)
     
CAPACITIES
Fuel tank12 gal (54 litres)
Cooling system16 pt. (9,1 litres)
Steering rack1/3 pt. (0,18 litre)
Engine - with filter8 pt. (4,54 litres)
Filter1/2 pt. (0.28 litre)
Gearbox and overdrive6 pt. (3,4 litres) E.R.90
Rear axle1 1/2 pt. (0,85 litre)

Enjoying this article? Our magazine is funded through the generous support of readers like you!
To contribute to our operating budget,  please click here and follow the instructions.
(Suggested contribution is twenty bucks per year. Feel free to give more!)

Torque Wrench Settings

ENGINElbf ftkgf m
Main bearing cap bolts - 1 to 4 537,32
Main bearing cap bolts - rear 689,40
Connecting rod cap nuts 334,65
Cylinder head bolts 689,40
Rocker shaft bolts 283,87
Flywheel bolts 557,60
Oil pump cover bolts 131,80
Oil pressure relief valve plug 334,56
Timing chain cover bolts 233,18
Crankshaft pulley bolt 15020,73
Distributor drive gear to camshaft bolt435,94
Exhaust manifold bolts 131,80
Induction manifold bolts 283,87
Induction manifold gasket clamp bolts131,80
Carburetter adapter nuts 182,49
       
Important : As the V8 engine is fitted with a cast aluminum cylinder block it is of critical importance to adhere to the specified tightening torque for all bolts. It is equally important to maintain the designed thread engagement lengths, otherwise irreparable damage may be done to the cylinder block. Always use bolts of the correct length and where specified use the thread lubricant and sealer.
       
REAR AXLE
Crown wheel bolts 638,70
Differential bearing cap bolts 537,32
Pinion bearing nut (new spacer only)20027,64
Half shaft nut 15020,73
       
REAR SUSPENSION
Shock absorber to side member nut 588,01
       
FRONT SUSPENSION
Bottom wishbone pivot to crossmember nut456,22
Front shock absorber to crossmember bolt446,08
Crossmember to side member nut - top557,60
Crossmember to side member nut - bottom456,22
       
STEERING
Column clamp bolt 850,98
Wheel nut 283,87
Column universal joint nut 212,90
Rack to tie rod ball joint nut 354,84
       
ROAD WHEELS
Stud nut 608,30


MGB-GT V8 ENGINES GENERAL DETAILS

ROCKER SHAFTS

Before removing the rocker shafts, note the position of the notch, arrowed, in the end face of each shaft. This notch must be uppermost and towards the front of the engine on the right hand side and towards the rear on the left hand side. After removing rocker shaft assemblies, withdraw the pushrods and tappets and retain in the sequence removed.

 

INSPECTION OF HYDRAULIC TAPPETS AND PUSHRODS

The tappets are non-serviceable. Replace tappet assembly if body is roughly scored or grooved, or has a blow hole extending through the wall in a position to permit leakage of oil from lower chamber of tappet. Inspect the cam contact surface of the tappets. Tappets must rotate and a circular wear pattern (as shown at "A") is normal. A non-rotating tappet will show wear as in the illustration (at "B"). Replace tappet and ensure that it is free to revolve in the cylinder block. "C" shows excessive wear of surface, and the tappet should be replaced. Pushrods, can be fitted either way round when new, but after use the rocker end of the rod becomes polished and should be retrofitted in the original position

NOTE

It should be noted that tappet noise can be expected on initial starting up after an overhaul due to oil drainage from the tappet assemblies or if the vehicle has been standing over a very long period. If excessive noise should be apparent alter an overhaul, the engine should be run at approximately 2500 rev/min for a few minutes when the noise should be eliminated.

 

INLET MANIFOLD

The inlet manifold is a one piece aluminium casting. This also contains water passages through which coolant circulates from the cylinder heads.

Also housed in the manifold is the thermostat, thermal transmitter for the temperature gauge, and the thermal switch which controls the electrically driven cooling fans.

A carburetter adaptor is mounted on the inlet manifold. This adaptor holds the carburetters, which are mounted at the rear of the engine.

Before refitting the inlet manifold, new gasket seals should be fitted. These must be smeared on both sides with silicon grease, then fitted in position ensuring that the ends of the seals are fitted correctly in the notches formed between the cylinder head and cylinder block.

Apply Hylomar sealing compound "SQ 32M" on the four corners of the cylinder head, inlet manifold gasket, and inlet manifold, around the water passage joints.

Place the inlet manifold gasket in position with the word 'FRONT' to the front, the open bolt hole 'A' will be positioned to the front, right band side.

Fit the gasket clamps and bolts but do not fully tighten at this stage.

Position the inlet manifold on the cylinder heads and connect up the water hoses.

Fit all bolts into the cylinder heads, using a little EC 776 lubricant/sealant. Note: The two longer bolts are installed at the front.

As the bolt holes are not at right angles to the inlet manifold's cylinder head faces, there may be an illusion of misalignment. Tighten all the manifold to cylinder head bolts a little at a time. Tighten evenly, alternating sides working from centre of engine to each end.

Finally tighten to a torque figure of 3,5 - 4,0 kgf m (25 - 30 lbf ft) following the sequence detailed above.

The clamp bolts at the front and rear of the gasket can now be tightened to a torque figure of 1,4 - 2,0 kgf m (10 - 15 lbf ft).

 

REFITTNIG EXHAUST MANIFOLD

It is essential that the following procedure is adopted. Locate the exhaust manifold on the engine. (No gasket is used.) Fit the fixing bolts, after coating with Loctite 40.

Tighten to torque figure 2,0 kgf m (15 lbf ft).

Do not overtighten at this stage.

After engine has run for a minimum of five minutes, torque settings should be rechecked. (The above procedure allows for "creep" due to different rates of expansion of dissimilar metals.)

CYLINDER HEAD

If both cylinder heads are being removed, mark them relative to LH and RH sides of the engine to ensure that they are refitted in their original position.

NOTE On stripping an engine, the cylinder head bolts should be immediately wire brush washed in 3M solvent No 2. If the bolts cannot be cleaned as soon as they are removed, it is essential that they be stored in a bath of trichiorethylene, petrol or paraffin etc., which may also be used as a cleaner if 3M solvent No. 2 is not available, otherwise the sealant used on previous assembly will tend to air harden making subsequent removal very difficult.

Fit new cylinder head gaskets with the word 'TOP' uppermost.

Do not use any sealant as the gaskets are already coated with a lacquer. Before refitting the cylinder head bolts, the threads should be cleaned, then coated with thread lubricant sealant 3M EC776.

Damage to the aluminium cylinder block threads can result if bolts are not lubricated with 'EC 776' prior to installation. A false torque reading may also be obtained.

Locate the cylinder head bolts in position:
Long bolts 1, 2 & 4,
Medium bolts 3, 5, 6, 7, 8, 9 & 10, and
Short bolts 11, 12, 13 & 14.

Tighten the bolts a little at a time in the sequence shown. Final torque: 9,0 to 9,6 kgf m (65 to 70 lbf ft). Uneven tightening of the cylinder head bolts can cause distortion of the cylinder bores, causing compression loss and excessive oil consumption,

CAUTION Any attempt to salvage the sparking plug threads in the cylinder head may result in breaking into the water jacket, rendering the head scrap.

Cylinder heads must not be refaced, as this will affect the fit of the induction manifold and also the operation of the hydraulic tappets.

CYLINDER HEAD OVERHAUL

Use particular care to protect gasket surfaces of cylinder heads.

After removing valves, clean with a soft wire brush. Avoid scratching the aluminium combustion chambers and valve seats.

If valve guides need replacing, they should be driven out using tool No. 274401.

Service valve guides are 0,025 mm (0.001 in.) larger on the outside diameter in order to obtain a good fit in the cylinder head.

Lubricate and install new guide from top of head using special tool No. 600959 'A' and distance piece part No, 605774 'B'.

The tool is designed to bottom when the guide is correctly positioned. The fitted guide should stand 19 mm (3/4 in.) above the step surrounding the valve guide boss in the cylinder head. See illustration "C".

Valve seat inserts are replaceable. For details see Repair Operation manual. Correct valve seat angle 46 degree + degree. Correct valve face angle is 45 degrees.

Improper hydraulic tappet operation may result if valve and seat are refinished to the extent that the valve stem is raised more than 1,27 mm (0.050 in.) above normal height. In this case, it will be necessary to grind off the end of the valve stem or replace parts. The normal height of the valve stem above the outer valve spring seat surface of the head is 47 mm (1.850 in.) + 0,635 mm (0.025 in.)

 

TIMING GEAR C0VER

Remove crankshaft pulley.

Mark the distributor body relative to the center line of the rotor arm. If the distributor is to be removed, make corresponding marks on the distributor and timing cover. Remove timing cover bolts, including two from the sump, and remove timing cover complete.

 

TIMING COVER OIL SEAL REPLACEMENT

Drive out oil thrower 'A' towards the rear of the cover. (It may be pulled out using 18G 1087.)

Coil a new seal "B" into a new oil thrower, refit thrower and seal assembly into timing cover, ensuring that the ends of the seal are at the top.

Stake the thrower in place by use of a small chisel at three equidistant points. Rotate a hammer shaft around the inside of the seal until the crankshaft pulley can be inserted.

 

REFITTING TIMING COVER

Fit new cover joint washer.

If distributor is in cover, set the rotor arm approximately 30 degrees before the final positioning mark, to compensate for skew gear engagement.

Locate timing cover in position.

Clean the threads of the cover securing bolts and then coat them with thread lubricant - sealant 3M EC 776.

Fit cover bolts and tighten to 2,8 - 3,5 kgf m (20 to 25 lbf ft).

Fit crankshaft pulley torque 19,3 to 22,3 kgf m (140 - 160 lbf ft).

CAMSHAFT

The camshaft is positioned centrally in the cylinder block and is supported by five bearings.

CAUTION: Do not damage the bearings when withdrawing the camshaft as the camshaft bearings are not serviceable.

TIMING CHAIN AND GEARS

An inverted tooth type chain is fitted in conjunction with a sintered iron crankshaft gear. The camshaft gear is made of aluminum alloy, the teeth are covered with nylon.

CAUTION: DO NOT rotate the engine after chain is removed if rocker shafts are fitted, otherwise the valve gear and pistons will be damaged.

REFITTING TIMING CHAIN AND GEARS

Remove the rocker shafts. Set the engine with the "number one piston" at TDC.

Temporarily fit the camshaft gear with the camshaft gear with the marking "FRONT" outward. (If the gear is not marked, the chamfer should be fitted towards the engine.)

Turn the camshaft until the mark on the gear is at the six o'clock position, then remove the gear without disturbing the camshaft setting. Locate the timing gears onto the chain with the timing marks aligned.

Engage chain and gears onto camshaft and crankshaft key locations.

Check that timing marks are in line. Fit the fuel pump cam "A" with "F" marking outward. (Note: It's used as a spacer only.) Fit the distributor drive "B", washer and bolt, and oil thrower, concave side outwards "C".

CONNECTING RODS AND PISTONS

Connecting rods have horizontally split big ends and plain small ends.

Pistons are of aluminium alloy with "W" slot skirt. These pistons must always be used with a crankshaft having an identification groove in the face at the starter dog end.

The piston gudgeon pins are a press fit in the small end of the connecting rod, known as semi-floating and are removed and refitted using tool No. 18G 1150 with adaptor 180 1150E.

After removing a connecting rod cap, screw guide bolts (part No 605351) onto the connecting rod.

Push the connecting rod and piston assembly up the cylinder bore and withdraw it from the top.

 

REFITTING

Turn the applicable crankshaft journal to BDC.

Place the bearing upper shell in the connecting rod.

Retain shell by screwing guide bolts onto the connecting rod.

Insert the connecting rod and piston assembly into its respective bore, noting that the domed boss on connecting rod ("A" on the illustration) and bearing cap ("B") must face towards the front of the engine on the right hand bank of cylinders and towards the rear on the left hand bank.

When both connecting rods are fitted, the bosses will face inwards towards each other.

 

BIG END BEARINGS

The fit of bearings to crankshaft is checked using Plastigauge - type PG-1 - part No. 605238.

Place a piece of Plastigauge across the centre of the lower half of the crankshaft journal, illustration "A". Locate the bearing cap and shell to the connecting rod.

Tighten the connecting rod cap nuts to torque figure 4,0 to 4,9 kgf m (30 to 35 lbf ft).

NOTE: DO NOT rotate the crankshaft while the Plastigauge is fitted.

Remove the bearing cap and shell.

Using the scale printed on the Plastigauge packet, measure the flattened Plastigauge at its widest point - illustration "B".

The graduation that most closely corresponds to the width of the Plastigauge indicates the bearing clearance.

The correct bearing clearance with new or overhauled components is 0,015 to 0,055 mm (0,0006 to 0.0022 in.).

If a bearing has been in service it is advisable to fit a new hearing if the clearance exceeds 0,08 mm (0.003 in.).

Wipe off the Piastigauge with an oily rag. DO NOT SCRAPE IT OFF.

CRANKSHAFT

Supported by five main bearings.

End-float 0,10 to 0,20 mm (0.004 to 0.008 in.) controlled by flanged centre main bearing.

NOTE: If the same bearing shells are to be refitted, retain them in pairs and mark them with the number of the respective journal.

Care must be taken when refitting main bearing shells regarding position in bearing. The shells with the oil drilling and oil grooves must be fitted to the cylinder block.

Main bearing clearance is checked using Plastigauge as detailed in connecting rod section of Student's Technical Notes.

 

CRANKSHAFT REAR OIL SEAL

A lip type seal is fitted into a recess formed by the cylinder block and the rear main bearing cap.

Bearing cap side seals of cruciform design are fitted into grooves in the sides of the cap. Illustration "B".

FITTING NEW REAR OIL SEAL

Fit new side seals to the grooves each side of the bearing cap. DO NOT cut the side seals to length, they must protrude 1,5 mm (0.062 in.) approximately above the bearing cap parting face.

Apply Hylomar PL 32M (Unipart No. GGC 102) to the rearmost half of the rear main bearing cap parting face or, if preferred, to the equivalent area on the cylinder block as iIlustrated at "D".

Lubricate the bearing shell and bearing cap side seals with clean engine oil.

Fit the bearing cap assembly to the cylinder block.

Do not tighten the fixings at this stage, but ensure that the cap is fully home and squarely seated or the cylinder block. Tension the cap bolts "A" equally by one quarter turn approximately, then back off one complete turn on each bolt.

Position the seal guide tool ("B") part No. R.O. 1014 on the crankshaft flange.

Ensure that the oil seal guide and the crankshaft journal are clean, then coat the seal guide and oil seal journal "C" with clean engine oil.

CAUTION: Do not handle the seal lip at any time, visually check that it is not damaged and ensure that the outside diameter remains clean and dry.

Position the oil seal, illustration "D", lipped side towards the engine, on to the seal guide.

Push home the seal fully and squarely by hand into the recess formed in the cap and block until it abuts against the machined step in the recess.

Withdraw the seal guide.

Tighten the rear main bearing cap bolts fully and evenly to torque figure 9,0 to 9,6 kgf m (65 to 70 lbf ft).



THE S.U. HORIZONTAL INTRGRAL FLOAT CARBURETTER (TYPE H.I.F.)

Pollution control limits required by appropriate legislation are becoming increasingly difficult to achieve.

The H.I.F. carburetter incorporates design features which will assist in reducing exhaust emissions to within the limits at present demanded.

The new design features provide:

(a) Automatic mixture adjustment relative to fuel temperature.
(b) Consistent accurate cold start mixture control.
(c) Improved idling mixture control and smoother progression characteristics.

The basic operation principles of the S.U. carburetter remain unchanged.

DESCRIPTION OF THE NEW DESIGN FEATURES

Piston and Main Body

The base of the piston now includes an horizontal slot. With the piston in position, this horizontal slot envelopes a box section cast in the throttle disc side of the venture bridge.

A drilling in the box section communicates with another drilling in the venture situated at the lower edge of the throttle disc. The slot in the piston, together with the two drillings, form a controlled by-pass mixture feed.

This new design feature provides better idling mixture control, and smoother progression characteristics.

The Needle

This is a spring-loaded type needle, biased in light contact with the jet, towards the throttle disc end of the carburetter, so providing a consistent crescent shaped fuel emission area.

To ensure maximum benefit from this new design feature, it is most important that the needle assembly is correctly fitted into the piston base.

The needle is correctly fitted when the etch line on the needle guide is nearest to, and centrally placed between the two transfer holes, and the needle shoulder flush with the piston base. The raised 'pip' on one end of the needle guide provides the bias.

This needle is not peculiar to the H.I.F. carburetter alone. It is currently fitted to the standard design S.U. carburetter fitted to some Home and Export model cars - e.g. 1750 Maxi and Marina range.

Float Chamber Components

The float chamber is an integral part of the carburetter body, providing a fuel reservoir in which the newly designed, one-piece, jet and feed pipe is partially immersed.

The horizontal link of the "L" shaped adjusting level is a bi-metal assembly submerged in the fuel and connected to the base of the jet. This bi-metal assembly senses changes in fuel temperature, and transmits the effects of these changes to the jet.

Ten degree variation in fuel temperature is equivalent to 0.004" to 0.006" jet movement.

This is an exhaust emission control design feature which provides automatic mixture control adjustment relative to fuel temperature.

Cold Start Enrichment Device

It has been established that the method of cold starting on the existing S.U. carburetter is inadequate to meet all current and future pollution control legislation, for the following reasons. The amount of "jet drop" provided for cold start is not under accurate control, permitting day to day variation of the mixture enrichment provided for cold start purposes. It has also been proved with the aid of highly sensitive exhaust gas analysers that the jet does not always return to its original position after the cold start operation has been completed.

The rotary valve type enrichment device fitted to the H.I.F. carburetter eliminates the jet movement discrepancies existing on other S.U. carburetters by providing an accurately controlled cold start mixture supply independent of the main jet.

This is yet another development by British Leyland in pursuing a policy of continuous improvement in the design and quality of its products.

September 1971
Product Training - Cars School.


L.H. OVERDRIVE

FAULT DIAGNOSIS

1. OVERDRIVE DOES NOT ENGAGE

Insufficient oil in gearbox.
Electrical fault.
Low hydraulic pressure.
Damaged parts within unit.

2. OVERDRIVE DOES NOT DISENGAGE

NOTE: If overdrive does disengage, do not reverse the car as extensive damage may result.

Electrical control system fault.
Sticking clutch.
Damaged parts within unit.

3. CLUTCH SLIP IN OVERDRIVE

Insufficient oil.
Low hydraulic pressure.
Worn or glazed clutch lining.

4. CLUTCH SLIP IN REVERSE OR FREEWHEEL CONDITION ON OVERRUN

Worn or glazed clutch lining.
Broken circlip on sunwheel.

5. NOISE IN OVERDRIVE ONLY

Epycyclic gear train worn.
Pump worn.

6. NOISE IN DIRECT DRIVE ONLY

Cone clutch bearing worn.

Product Training (Cars)
October 1972


GEARBOX

GEARBOX - NOTES FOR INSTRUCTORS

DIFFERENCES

The gearbox assembly fitted to the MGB GT V8 is very similar to the MGC box and the gear cluster is similar to the MGB.

The main differences are as follows:

The clutch release lever is different, being shaped to accommodate a steel sleeve and ball race thrust bearing which is similar in appearance to that used on the Morris Marina.

The front cover incorporates an extended nose which supports the release bearing and sleeve.

The laygear thrust washers have been altered from round steel washers with oil grooves to dimpled, copper covered thrust washers with tabs locating against webs inside the gearbox case.

GENERAL

The two synchronizer hub assemblies are not interchangeable.

The coupling sleeve of 3rd/4th synchro hub has a groove machined around it as identification.

If both forks are fitted against the coupling sleeves the difference in diameter will he obvious. It is most obvious when 1st/2nd selector fork is fitted against 3rd/4th hub.

The third motion shaft lock washer tabs fit into the recessed nut.

Second gear thrust washer has two internal splines, locking it to the shaft.

Third gear end float must be checked with a D.T.I., as the thrust washers fit into recesses in the gear, preventing the use of feeler gauges.

Product Training (Cars)
June 1973

GEARBOX

DATA

First motion shaft hearing nip0 to 0.001 in. (0 to 0,03 mm)
Shims available0.002 in. (0,05 mm), 0.004 in. (0,10 mm)
Gear endfloat - 1st and 3rd0.005 to 0.007 in. (0,13 to 0,18 mm)
Gear endfloat - 2nd0.005 to 0.008 in. (0,13 to 0,20 mm)
Laygear endfloat0.002 to 0.007 in. (0,05 to 0,18 mm)
Laygear selective thrust washers (rear)0.1195 to 0.1215 in. (3,04 to 3,09 mm)
0.123 to 0.125 in. (3.12 to 3.17 mm)
0.1265 to 0.1285 in. (3.21 to 3.26 mm)
0.130 to 0.132 in. (3,30 to 3,35 mm)
0.133 to 0.135 in. (3,38 to 3,43 mm)
Synchromesh hub spring - free length0.720 in. (18,3 mm)
Selector detent spring - free length1.0625 in. (30,2 mm)
Reverse plunger spring - free length0.9603 in. (23,02 mm)

DISMANTLING PROCEDURE

Front cover

Dislodge the clutch release lever rubber boot from the flywheel housing.

Remove the release lever pivot bolt and withdraw the lever complete with the bearing and sleeve.

Remove the front cover.

Note the shims fitted between the cover and the first motion shaft bearing.

Overdrive and adaptor

Undo the six retaining bolts and remove the remote control assembly.

Remove the overdr:ive assembly from the gearbox adaptor.

Slide the overdrive pump cam off the tail shaft and remove the driving ball. Using 18G 1004 (see fig 2) remove the cam circlip from the shaft.

Engage 4th gear.

Withdraw the selector interlock arm and plate assembly (see fig 3), tilting the assembly as necessary.

Remove the adaptor from the gearbox.

Check the operation of the reverse plunger, reverse light switch and the overdrive isolation switch.

 

Selector forks and rods

Remove the side cover.

Remove the three selector detent plunger plugs and springs (see fig 4).

Slacken the locknuts (7/l6 A.F.) and undo the fork retaining screws (1/8 Whit.)

Withdraw the selector rods and remove the forks.

If it is only necessary to remove the selector forks and rods, this can be done by following the above procedure from the heading 'Overdrive and adaptor' without removing the gearbox from the engine.

 

Reverse idler gear

Knock back the locking tab on the shaft retaining bolt, remove the bolt and withdraw the shaft rearwards.

Withdraw the gear from the case.

Inspect the shaft, gear teeth and gear bearings for signs of wear or damage.

First motion shaft

Carefully drift the layshaft from the gearbox forwards.

Check that the laygear teeth are clear of the gear.

Fit the impulse extractor 18G 284 with adaptors 18G 284 AAA and 18G 284 AW and remove the first motion shaft assembly.

(First motion shaft dismantling described on page E4.)

Third motion shaft

Again, check that the laygear teeth are clear of the gears and synchro hubs.

With the aid of hollow drift 18G 1045, remove the third motion shaft rearwards from the gearbox.

Note the locating peg and the cut-away in the bearing flange which locates over it.

(Third motion shaft dismantling described on page E4.)

 

Laygear

Temporarily refit the layshaft and check the laygear end float, which should be 0.002 to 0.007 in. (0,05 to 0,18 mm).

Remove the layshaft.

Remove the laygear and thrust washers. Rear washer is selective.

Check the layshaft, the laygear teeth and the laygear bearings for wear or damage.

FIRST MOTION SHAFT DISMANTLING

Withdraw the caged needle roller bearing from inside the rear end of the shaft.

Knock back the hearing nut, Iock washer tab and fit tool 18G 49 to the nut.

Clamp the shaft in a soft jawed vice (aluminium faced).

Remove the nut (L.H. thread) and the lock washer, then press the bearing from the shaft.

Inspect the shaft and the bearing for signs of wear or damage.

THIRD MOTION SHAFT DISMANTLING

Check the end float of first and second gears with feeler gauges and the end float of third gear with a dial test indicator (D.T.I.). See data for correct end float.

Remove the 3rd/4th synchro. hub assembly complete with baulk rings. (Note the annular groove on the coupling sleeve.)

After knocking back the lockwasher tab remove the round nut from the front of the shaft using 18G 1024 then remove the lock washer.

Remove the shaft sleeve, third speed gear and the interlocking thrust washer.

Remove second speed gear and its thrust washer.

Remove the lst/2nd speed synchro. hub assembly complete with baulk rings.

Note: Although the components of the two synchro. hub assemblies look similar, none of them are interchangeable from one hub to the other. (See right, for identification of baulk rings.)

After knocking back the lock washer tab use 18G 391 (see right) to remove the rear shaft nut.

Having removed the nut and lock washer remove the distance tube from the shaft.

Press he first speed gear, reverse gear and the bearing complete with housing from the shaft.

Wrap a cloth loosely around the synchro. hub assembly to retain the balls and springs and push the hub out of the coupling sleeve.

Check the gears, hubs, coupling sleeves, shaft and bearing for wear or damage. Also, if the gear endfloat was excessive check the gear thrust washers for wear.

 

 

REASSEMBLY PROCEDURE

Replace any components found to be worn or damaged.

THIRD MOTION SHAFT

Use 18G 1026 to reassemble the synchro. Hubs. The hub may face either way inside its own coupling sleeve but do not interchange them.

Press the first speed gear, reverse gear and bearing onto the shaft.

Refit the distance piece and a new Iock washer, then tighten the nut with 18G 391.

Refit the 1st/2nd synchro. hub assembly. The assembly may face either way but remember to fit the correct baulk rings with it.

Refit the thrust washer and second gear.

Refit third gear to the shaft sleeve and fit the interlocking thrust over the tangs on the sleeve, then fit the assembly to the shaft.

Fit a new lock washer, tighten the nut with 18G 1024 and lock with the lock washer.

Refit the 3rd/4th synchro. hub complete with baulk rings.

FIRST MOTION SHAFT

Press the bearing onto the shaft.

Fit a new lock washer and refit the nut. Clamp the shaft in a soft jawed vice (aluminium faced), tighten the nut with 18G 49 and lock with the lock washer.

Insert the needle roller bearing into the rear end of the shaft.

GEARBOX REASSEMBLY

Laygear

If the laygear end float is outside the limits given in the dismantling procedure select thrust washers.

Fit the laygear with bearings and thrust washers and lay it in the bottom of the gearbox.

Third motion shaft

Enter the assembled shaft into the gearbox from the rear.

Check that the laygear teeth are clear of the shaft gear teeth.

First motion shaft

Carefully drift the assembled shaft into the casing, ensuring that the laygear teeth do not foul the shaft gear teeth.

The layshaft can now be refitted from the front. Note: cut-away locates in front cover.

Reverse idler gear

Place the gear into the gearbox.

Fit the shaft aligning the dowel hole with the locating bolt hole.

Fit the dowel bolt with a new tab washer, tighten the bolt and lock with the tab.

Selector forks and rods

Fit the selector forks over the synchro. hubs and reverse idler.

Clean any burrs from the rods at the fork location points.

Ensure that the detent plungers are clear of the rod holes and refit the rods.

Tighten the fork retaining screws and lock the lock nuts.

Refit the selector detent springs and plugs.

Refit the side cover,

OVERDRIVE AND ADAPTOR

Refit the adaptor to the gearbox.

Engage 4th gear.

Refit the overdrive pump cam circlip to the shaft using 18G 1004. Refit pump cam driving ball to the shaft then fit the cam over it. Rotate the gearbox mainshaft until the lowest point of the pump cam is nearest to the pump plunger. This is to enable the plunger to ride over the cam.

Refit the overdrive to the adaptor.

Refit the remote control assembly.

FRONT COVER

Measure the depth of the register in the front cover "A".

Measure how much the first motion shaft bearing outer race protrudes from the casing "B".

Calculate the thickness of shims required between the front cover and bearing as in the following example:

Front cover gasket (compressed thickness) = 0.015 in. (0,38 mm)

plus (+) shim register depth of 0.228 in. (5,79 mm)

equals (subtotal) 0.243 in. (6,17 mm)

minus (-) bearing protrusion of 0.218 in. (5,54 mm)

Equals (total) 0.025 in, (0,63 mm)

The shim thickness required is the calculated figure
+ 0.001 in. (0,03 mm) for bearing 'nip'.

Shims are available in the following sizes: 0.002 in. (0,05 mm) and 0.004 in. (0,10 mm).

Fit new front cover gasket.

Fit the front cover, ensuring that the shims are properly positioned, and tighten the nuts.

Coat the clutch lever pivot bolt and the rear half of the clutch release bearing bore with Duckhams Laminoid grease or the equivalent.


BritishV8 Magazine has assembled the largest, most authoritative collection of MG "MGB GT V8" information you'll find anywhere. Check it out!   Access our MGB GT V8 article index by clicking here.


British V8 Home:        Read the Magazine        Photo Gallery        Web Forum        Annual Meets        Contact Us        Site Map