The article below was published in "Practical Motorist and Motor Cyclist" over two issues dated January 1956 and February 1956 and covers "Overhauling the Morris 10 series M

Overhauling the Morris 10 series M

Main Features of the Engine Discussed and Methods of Decarbonising The Fitting of Valve Spring Seals and Valve Guides and Servicing Details of the Carburetter By "AUTOMOBILIST"

The main features of the Morris Ten Series “M” o.h.v. engine closely resemble those of the M.G. models, and develop 37 b.h.p. at 4,600 r.p.m.
Fig. 1 shows a section of the engine from which many of its features can be seen. The camshaft is arranged on the nearside at the base of the cylinders and drives the externally mounted oil pump through helical gears. Tappets take the thrust of the cams, operating overhead rockers through push rods. The valves are slightly inclined from the vertical as seen from front or back of the engine and double springs are employed. The crankshaft has counterbalances webs, while the connecting rods have square-jointed big-ends (not angular) and clamped-type small ends for the gudgeon pins. The crankshaft runs in three main bearings, carrying a flange-mounted flywheel at the rear, and a sprocket for a double-roller chain driving the camshaft at the front, the chain on the later models having a tensioner.
Outside the timing case the crankshaft pulley, taking a vee-belt which is triangulated round the dynamo and water pump – this being mounted on the front of the cylinder block and incorporating the fan. The crankshaft is sealed behind the rear main bearing by means of an oil slinger and a return thread. The slinger throws oil into an annular recess from with it drains through a large-bore pipe into the sump; and the return thread runs in a close-fitting bore formed partly by the main bearing housing and partly by a small cover attached to the rear of the crankcase.
At the front the seal is made by halved graphite-asbestos packings, one-half in the timing case, the other in the sump, which are renewable. The sump is sealed on the housing by a cork strip in the semicircular recess.

Lubrication System

The gear-type oil pump on the side of the crankcase takes its supply from the sump, where there is a gauze strainer to exclude particles of carbon or other foreign matter. From the pump the oil is forced to a filter of throw-away type. Thence the oil enters a horizontal gallery running the length of the crankcase, front to rear.
From the gallery, through drilled passages, are fed the rear main bearing and camshaft bearing, the centre main bearing and camshaft bearing. A feed from the chain tensioner lubricates the timing chain. The big-ends are supplied through holes drilled in the crankshaft, fed from the main bearings, surplus oil flung out lubricating camshaft, pistons and cylinders.
From the rear of the gallery there is a feed through an external pipe to the cylinder head. Passing through the drilled holes in the cylinder head and the rear bracket of rocker shaft the oil enters this shaft, which is hollow and provided with drilled ways for rocker bush lubrication. From the rockers the oil then returns to the sump.
In the pump body is a relief valve which operates when the pressure exceeds 75lb per sq. in., and in the face on the cylinder block there is a by-pass valve to ensure that I the event of the throw-away filter becoming blocked oil will be fed direct to the main horizontal gallery. Normal oil pressure is 40lb. per sq. in., falling to about 20lb. at tick-over.
Including the filter early engines hold 6½ pints of oil and later engines 9 pints; in each case this includes 1 pint for the filter. Oil should be changed at 500 miles afer an overhaul, and afterwards at intervals of 3,000 miles. The filter should be renewed at 12,000 miles.

Servicing Operations

Points in the anti-clockwise automatic-advance distributor should be set to .010in. to 0.12in., and the gaps of the Champion L.10 - ½ in. reach plugs to .018in. to .022in. Ignition timing is T.D.C., fully retarded.
With the rotor arm removed, a few drops of light oil may be applied to the centre of the shaft and a trace of grease or oil may be applied to the cam and the rocker arm pivot. A few drops of light oil may also be run through the base of the contact breaker (past the cam) for lubricating the automatic-advance mechanism. Should there be a squeak from the distributor it may be the centre brush, to which a smear of grease or oil should be applied where it bears on the rotor arm.
It is recommended about every 1,000 miles to remove the brass cap nut from the carburetter suction chamber and pour in about a teaspoonful of good quality 20 grade oil to supply the dash pot.
Valve clearances are set on the overhead rockers when the cover has been removed. This should be done with the engine hot from a run, the correct clearance for both inlet and exhaust then being .019in.
To ensure that each tappet is on the back of its cam during adjustment, the engine can be turned for the cam to open the valve fully, then from this position, noting the attitude of the starting handle, the engine should be rotated one complete turn. Alternatively, reference may be made to the following sequence for setting:
Adjust No. 1 rocker with No. 8 valve fully open. Adjust No. 5 rocker with No. 4 valve fully open. Adjust No. 2 rocker with No. 7 valve fully open. Adjust No. 8 rocker with No. 1 valve fully open. Adjust No. 6 rocker with No. 3 valve fully open. Adjust No. 4 rocker with No. 5 valve fully open. Adjust No. 7 rocker with No. 2 valve fully open.