MG Midget Technical specs.
PLEASE NOTE: These specifications are specific to my model year midget, my engine type and my tastes.
More detailed Tech Specs for ALL 1275cc Spridgets can be found at www.spridget-tech.com where a vast compilation of all years of Spridgets and motors can be found. Credit to Chris S for putting all that together.
I am not a professional mechanic, I certainly don't claim to be, nor am I an attorney, so use the data provided at your own risk because I'm not responsible if you torque your thermostat housing nuts to 200 lbs/ft, causing damage that results in a loss of coolant and a cracked cylinder head, and very expensive repairs. This is collection of data from multiple sources which I use for 'at a glance' reference when I'm tinkering in my garage which is a hobby, just like stamp collecting or fishing.
BTW, I don't collect stamps or fish, just an example of 'hobby', the only thing I collect is cholesterol.
| Technical Specifications | ||||||||
| Firing Order | 1-3-4-2 | |||||||
| Valve Clearance | 0.012 | Cold | ||||||
| Idle Speed | 1000 | rpm | ||||||
| Static Timing | 7 | BTDC | ||||||
| Dynamic Timing | 13 | BTDC @ 1000 rpm | ||||||
| Timing mark location | Timing cover, bottom | |||||||
| Distributor type | Lucas 25D | Contact points | ||||||
| Points Clearace | 0.014 to 0.16 | |||||||
| Rotor direction | Anti-clockwise | |||||||
| Dwell angle | 60 | |||||||
| Coil | Lucas | |||||||
| Primary Resistance | 3 to 3.4 | Ohms | ||||||
| Spark plug gap | 0.24 to 0.26 | |||||||
| Carburetor | 2 X | SU HS2 | 20 W/ 50 | |||||
| Carburetor main jet | 90 | |||||||
| Carburetor jet needle | ABC | |||||||
| Engine type | 1275cc | OHV | 4 - cyl | |||||
| Compression ratio | 8.8:1 | High compression | ||||||
| Engine bore | 2.78 | inches | ||||||
| Engine stroke | 3.2 | inches | ||||||
| Oil press Idle | 20 | lbs | ||||||
| Oil press Normal | 40 to 70 | lbs | ||||||
| Fuel pump | SU AUF216 | |||||||
| Drivebelt tension | 0.5 | inches | 13mm | |||||
| Fuel Tank Capacity | 8.6 | US Gallons | High Octane with Lead substitute | |||||
| Cooling System Capacity | 7 | US Pints | 50/50 | |||||
| Cooling Filler cap press | 15 | lb/ft | ||||||
| Sump Capacity | 7.8 | US Pints | 20 W/ 50 | |||||
| Gearbox Capacity | 2.7 | US Pints | 20 W/ 50 | |||||
| Rear Axle Capacity | 2.1 | US Pints | 90EP | |||||
| Engine Data | ||||||||
| Crankshaft and Main Bearings | ||||||||
| Main journal diameter | 2.0005 to 2.0010 | inches | ||||||
| Main bearing length | 0.975 to 0.985 | inches | ||||||
| Crankpin journal diameter | 1.6254 to 1.6259 | inches | ||||||
| Main bearing diam clearance | 0.0010 to 0.0027 | inches | ||||||
| Connecting rods and Big-End Bearings | ||||||||
| Length b/w centers | 5.748 to 5.792 | inches | ||||||
| Big-end bearing length | 0.840 to 0.850 | inches | ||||||
| Endfloat on crankpin | 0.006 to 0.010 | inches | ||||||
| Big-end diam clearance | 0.0010 to 0.0025 | inches | ||||||
| Gudgeon Pin type | Interference | Hand push | ||||||
| Gudgeon Pin diameter | 0.8123 to 0.8125 | inches | ||||||
| fit to con-rod | 0.0008 to 0.0015 | inches | ||||||
| Pistons - Aluminium, solid skirt, dished crown | ||||||||
| clearance bottom of skirt | 0.0015 to 0.0021 | inches | ||||||
| clearance top of skirt | 0.0029 to 0.0037 | inches | ||||||
| Piston Rings | ||||||||
| Compression rings - type | Top | Internally chamfered, chrome | ||||||
| 2nd and 3rd | Tapered, cast iron | |||||||
| width all | 0.615 to 0.625 | inches | ||||||
| Fitted gap | Top | 0.011 to 0.016 | inches | |||||
| 2nd and 3rd | 0.008 to 0.013 | inches | ||||||
| Ring to groove clearance | 0.0015 to 0.0035 | inches | ||||||
| Oil control ring - Duraflex 61 | ||||||||
| Fitted gap | 0.012 to 0.028 | inches | ||||||
| Valve Data | ||||||||
| Intake | Head diameter | 1.307 to 1.312 | inches | |||||
| Exhaust | Head diameter | 1.1515 to 1.565 | inches | |||||
| Intake | Stem diameter | 0.2793 to 0.2798 | inches | |||||
| Exhaust | Stem diameter | 0.2788 to 0.2793 | inches | |||||
| Stem to guide clearance | 0.0015 to 0.0025 | inches | ||||||
| Valve to rocker clearance | 0.012 | inches | cold | |||||
| Valve Springs | ||||||||
| Free length - inner | 1.703 | inches | ||||||
| Free length - outer | 1.828 | inches | ||||||
| Valve lift (intake & exhaust) | 0.318 | inches | ||||||
| Vavle guides | ||||||||
| Length | Intake | 1.6875 | inches | |||||
| Length | Exhaust | 1.6875 | inches | |||||
| Fitted height above seat | 0.540 | inches | Intake & Exhaust | |||||
| Valve Timing | ||||||||
| Timing marks | dimples on timing gears | |||||||
| Rocker clearances | 0.029 | inches | timing only | |||||
| Intake opens | 5 | BTDC | ||||||
| intake closes | 45 | ABDC | ||||||
| Exhaust opens | 51 | BBDC | ||||||
| Exhaust closes | 21 | ATDC | ||||||
| Torque Settings | ||||||||
| Cylinder Head Nuts Plain | 42 | Ft/lbs | ||||||
| Cylinder Head Nuts Stamped '22' | 50 | Ft/lbs | ||||||
| Con-rod nuts Plain | 40 | Ft/lbs | ||||||
| Con-rod nuts Nyloc | 32 | Ft/lbs | ||||||
| Crankshaft pulley bolt | 70 | Ft/lbs | ||||||
| Flywheel bolts | 40 | Ft/lbs | ||||||
| Main bearing bolts | 60 | Ft/lbs | ||||||
| Manifold nuts | 15 | Ft/lbs | ||||||
| Oil filter retaining nuts | 16 | Ft/lbs | ||||||
| Oil pipe union adapter | 20 | Ft/lbs | ||||||
| Rocker cover retaining bolts | 4 | Ft/lbs | ||||||
| Rocker pedestal nuts | 25 | Ft/lbs | ||||||
| Sump retaining bolts | 6 | Ft/lbs | ||||||
| Thermostat housing nuts | 8 | Ft/lbs | ||||||
| Timing cover 1/4 inch bolts | 6 | Ft/lbs | ||||||
| Timing cover 5/16 inch bolts | 14 | Ft/lbs | ||||||
| Water pump nuts | 17 | Ft/lbs | ||||||
| Fan securing bolt | 8 | Ft/lbs | ||||||
| Fuel tank drain plug | 9 | Ft/lbs | ||||||
| Mechanical fuel pump to block | 14 | Ft/lbs | ||||||
| Spark plugs | 20 | Ft/lbs | ||||||
| Rear extension to gearbox bolts | 18-20 | Ft/lbs | ||||||
| Drive flange nut | 90-100 | Ft/lbs | ||||||
| Brake disc to hub | 43 | Ft/lbs | ||||||
| Brake caliper to stub axle | 48 | Ft/lbs | ||||||
| Brake pressure failure warning valve & plug | 16 | Ft/lbs | ||||||
| Alternator pulley nut | 25 | Ft/lbs | ||||||
| Starter motor retaining nuts | 34 | Ft/lbs | ||||||
| Steering column upper fixing bolts | 12-17 | Ft/lbs | ||||||
| Steering column pinch bolt | 9-12 | Ft/lbs | ||||||
| Steering rack housing clamp bolts | 20-22 | Ft/lbs | ||||||
| Steering rack mounting bracket bolts | 17-18 | Ft/lbs | ||||||
| Tie rod ball joint nut | 28-32 | Ft/lbs | ||||||
| Tie rod end assembly locknut | 30-35 | Ft/lbs | ||||||
| Tie rod rack locknut | 80 | Ft/lbs | ||||||
| Front & Rear damper bolts | 25-30 | Ft/lbs | ||||||
| Front hub castellated - Disc | 55-65 | Ft/lbs | ||||||
| trunion retaining nut | 40 | Ft/lbs | ||||||
| Steering wheel nut | 37 | Ft/lbs | ||||||
| Roadwheel lug nuts | 45 | Ft/lbs | ||||||
| Back to Top | Back to Main |