Morris Oxford MO
Reviewed by Unique Cars and Parts
Our Rating: 2
By the late 1940's Morris desperately needed new models to put on the showroom floor. The cheaper and more economical version was to become immensely popular, the Morris Minor MM, but the Oxford made its debut at the same time and has, for those that are not Morris fans, become somewhat forgotten. Aimed fairly and squarely at the family man, the Oxford featured an all new unit construction four door body very similar in appearance to its smaller stable-mate.
This new body shell was also used as the base for other "Nuffield" cars including the Morris Six, Wolseley 4/50 and 6/80. Other new features included the Minor style torsion bar suspension
, a column gear change and a "new" side-valve four cylinder engine which many viewed as a retrospective move (the out-going Morris Ten used an overhead valve layout!). The Oxford MO remained in production in both Saloon and Traveller forms until the arrival of the Series II in 1953.
Morris Oxford Series II
The update to the Morris Oxford featured a new grille and modifications to the specifications the new Morris Oxford was greatly improved in appearance with its "new look" for 1953
. The new grille was in pressed steel and chromium-plated in a completely different design to the previous die-cast zinc-alloy type. The new grille was made in two pieces, something the designers had been asked for by owners who had suffered minor front-enders, so that the cost of repairs would be cut significantly should only one part be required for replacement.
Mechanical changes included the damper to the rack and pinion steering, which was improved to help eliminate the transference of road shocks to the steering wheel. To improve the already fine handling characteristics of the Oxford the manufacturers fitted larger shock absorbers to the front torsion bar suspension. The starter switch has been slightly altered to avoid jamming and the handbrake has been modified for more effective action. More attention was paid to rust-proofing by a "bonderizing" process and the use of chromium plating for the window was abandoned in favour of stainless steel. The engine fitted to the Series II Morris Minor was manufactured by the British Motor Corporation and was the same unit as installed in the Austin A30 and Morris Minor Series II.
One Of The Last With A Sidevalve Engine
The Oxford was one of the last medium-sized cars to employ a side valve engine, but perhaps that was a good thing, as the Series MO Morris was well known as a reliable performer. Features of the four-cylinder engine included a single plate dry clutch and a four-speed gearbox. The robust four throw crankshaft was carried in three renewable white metal steel-backed bearings fitted without shims. The big-end bearings were also of this type. Pistons were of tin-plated aluminium alloy and had two compression rings and one oil control ring. Three bearings supported the camshaft which was driven by helical gears. Valves
were operated by cast tappets located in guides cast integrally with the block. Tappet adjustment was by orthodox tappet head screw and locknut.
Servicing the MO Yourself
Early models were cooled by thermo syphon action, assisted by an impellor and fan. Later, a six-bladed fan and closed circuit for the cooling water was provided. To remove the cylinder head
for decarbonising or any other operation, commence by draining the cooling system. Drain taps are located on the left side of the radiator bottom tank under the bumper and on the right side of the engine at the centre of the block. Earlier models have the drain tap at the rear on the left
Disconnect the top water hose and the positive battery
lead. Detach the throttle return spring from the air cleaner pipe and by slackening the locknut release the throttle cable from the throttle lever. Withdraw the cable from the bracket on the cylinder head
Remove the air cleaner, then disconnect the low tension wire from its terminal on the side oi the distributor. Mark each plug lead to assist in their correct installation, then disconnect then: from the plugs. Remove the distributor cover with the high tension leads attached.
Note the graduations on the cylinder head
and the mark on the distributor body, in particular, the exact position of the distributor in the cylinder head
. This will facilitate replacement. Slacken the distributor clamp cotter nut in the lug on the side of the head and tap back the cotter (early models have a bolt and split lug). Remove the distributor. Slacken the cylinder head
nut studs half a turn at a time until they are all free. This will avoid possible distortion of the head. Completely remove these nuts, then lift off the head.
Replacement of the head is a reversal of the above process. Take care to ensure that the distributor shaft tunnel in the head and block are correctly aligned. A special alignment gauge is best but if one of these is not available, use the distributor. Insert it in the shaft housing before the head is tightened down. When tightening the distributor clamp bolt in the split lug on early models, do not overtighten or the lug may break, necessitating the fitting of a new cylinder head
. Tighten the head bolts in the approved order and tighten again when the engine is hot.
The S.U. carburettor
The tuning of the S.U. carburettor was simplicity itself if it is thoroughly understood that all jets are of standard size. The only adjustment possible was fitting the right size of needle with the jet adjusting nut set correctly for idling. It cannot be emphasised too strongly that it is of no use whatever trying to adjust the carburetter in any other manner. It is of the utmost importance that the carburettor should be adjusted by means of the jet and jet adjusting nut in such a way that the correct mixture is obtained when the engine is idling - that it to say, it should be made to fire as evenly as possible. This can be noted by listening to the exhaust
. If the engine has a constant uneven beat (known as "hunting"), this is due to rich mixture. If the exhaust
note is irregular and splashy, the mixture is too weak. This adjustment not only adjusts the carburetter for idling, but for the whole range of speeds.
If this adjustment is not made, consumption will be bad and probably the performance poor. Should your car, therefore, not be satisfactory in respect to consumption or performance look to this adjustment, and if the correct size needle is fitted it will put the matter right. To adjust, run the engine until it attains its normal running- temperature. Adjust the jet to such a position that the engine idles on the correct mixture. An easy way to do this is to adjust the t jet up to a weaker position, then unscrew the jet adjusting nut until it brings the jet down to the position where the engine idles with an even exhaust
A simple way to test for rich mixture when the engine is idling is to lift the piston up slightly, say 1/32 in., and if when this is done the engine runs faster, the mixture is too strong. If, after this adjustment has been made, the road performance is not satisfactory, a larger or smaller needle will be necessary, as the case may be. If the car pulls better with the manual mixture control pulled out, a smaller needle is required.
- Inspect oil level in engine and replenish if necessary every 250 miles.
- Examine water level in radiator and top up each week.
- Grease fan shaft every 500 miles.
- Grease king pins every 500 miles.
- Grease steering knuckles every 500 miles.
- Grease universal joints every 6,000 miles.
- Grease sliding joint on propellor shaft every 1,000 miles.
- Check oil level in gearbox with dipstick and replenish if necessary with hypoid oil every 1,000 miles.
- Replenish differential oil if necessary avery 1,000 miles.
- Remove brass cap from top of carburetter suction chamber and add teaspoon of engine oil every 1,000 miles.
- Inspect fluid level in master brake cylinder every 1,000 miles and replenish if necessary with Lockheed No. 5 Fluid.
- Grease tie rod shaft every 500 miles.
- Drain oil and refill with fresh oil every 5,000 miles.
- Remove air cleaner, clean bowl and mesh and refill to indicated level every 3,000 miles.
- Lightly oil distributor rotor arm, advance mechanism and spindle every 3,000 miles.
- Remove generator grease cap and refill with grease every 3,000 miles.
- Drain and refill gearbox every 6,000 miles.
- Drain and refill differential every 6,000 miles.
- Check tyre-pressures weekly, including spares.
- Clean out duct from air cleaner to carburetter every 12,000 miles.
- Clean shock absorbers thoroughly and refill if necessary every 12,000 miles.
- Renew oil filter element every 12,000 miles.
- Grease steering box every 12,000 miles.
Morris Oxford Quick Specifications:
Bore and Stroke - 2.894 in. (73.5 mm.) x 3.425 in. (87 mm.). No. of compression rings - 2. Width of compression rings - 2 mm. (.078 in.). No. of oil rings 1. Width of oil rings - 3.97 mm. (.156 in.). Ring gap- .002 in-. 006 in. (comp.) ; .006 - .010 in. Oil pressure, lb. sq. in. - 60 lb. sq. in. Valve timing markings - "T" marks on gear Exhaust valve diam. - Head and Stem-Head, 1.1 : Stem, .312 in. Inlet valve diam. - Head and Stem-Head, 1.283 in. Stem, .312 in. Valve seat angle - 45 degrees. Inlet valve clearance for timing .022 in. (for inlet valve to open at T.D.C.). Inlet valve opens degrees - 8 deg. B.T.D.C. Inlet valve opens - No. of flywheel teeth - 2.87 2.87 teeth. Inlet valve opens - piston traverse - .020 in. before. Inlet valve working clearance-.015 in. hot. Exhaust valve working clearance-.015 in. hot. Piston clearance top-.001-.002 in. Piston clearance bottom-.0008 in. (.020 mm.). Firing order-1, 3, 4, 2.
S.U. lg in. horizontal. All settings-Needles-Rich, E.S.; Standard. 7 7 Weak, H.B.
Breaker gap-.010-.012 in. Plug--14 mm. Plug gap-.018-.022 in. Ignition timing-degrees-T.D.C. (final setting by road test). Battery-capacity and type-51 amp./hr. 12 volt. Battery earth-positive or negative-Positive. Distributor rotation-Anti-clockwise. Automatic advancer-22 degrees on crankshaft.
Clutch and Gearbox:
Gear ratios-Top, 1.00:1; Third, 1.358:1; Second, 2.071:1; First, 3.5:1; Reverse, 3.5:1. Clutch type - Borg & Beck 7.5 in. A6-G Dry Plate. Type of facing-Borg & Beck composite.
Track-53 in. (1.346 in.). Turning circle-36 ft. (11 mm.). Tyre size and pressures-5.25 x 15 in. Front, 24 lb.; Rear, 24 lb. Timber-Vertical to % deg. positive. Caster angle-3 degrees. Toe-in-Parallel. King pin inclination-9 degrees.