Morris Minor Owners Club Series MM Register

Technical Information

Disclaimer:
Information on this website is given in good faith and whilst every effort is made to check its accuracy anyone using said information does so at their own risk, and liability cannot be accepted for loss or damage incurred through use or misuse of aforementioned information.

1. Series MM Engine information (Torque settings, etc)

2. Morris Minor Paint Colour Codes

3. Commercial Colours Only

4. Ex Military Generator Engines

5. Swivel Pin Modification

6. Front Suspension Stub Axle and Wheel Bolt Threads

7. Combined Indicator and Trafficator Wiring Diagram

The torque settings for the Series MM engine are as follows:

Cylinder Head Bolt  Tightening Order:

Front of Engine

MORRIS MINOR PAINT COLOUR CODES

* Contact Registrar for suppler

COMMERCIAL COLOURS ONLY

Ex Military Generator Engines

A quantity of ex military generator engines from various sources has been coming onto the market over the last few years, and whilst they provide a useful supply of engines for the Series MM Minor, their fitting is not quite as straightforward as may at first appear.

The engine is basically of the USHM3 type of block as fitted to the later Series MMs and was used as an auxiliary generator engine in the Centurion tank when the vehicle was stationary.

The useable parts of the engine are confined to the cylinder block, crankshaft, pistons, timing gear, camshaft, and valve assembly and so a donor engine will be required to supply the remaining parts.

The engines may vary in detail as to the fitting of external components but I shall attempt to go through the various points to be noted when fitting these engines.

Various claims are made as to the condition of these engines, such as “very little used”, “recently overhauled” etc. From experience a precautionary strip down and inspection is recommended, mine was heavily coked up and the pistons were fitted the wrong way round.

The engines are often supplied with extra external pipework and bolt on accessories which will need to be removed.

The cylinder head is of a completely different design and will be of no use in a car; however if you know someone with a President tractor or a side valve Vedette marine engine they may be grateful for a spare cylinder head. In order to fit the correct cylinder head of either the early or later type the centre and right hand rows of cylinder head studs will need to be changed for those of the correct length. The distributor and spark plugs will need to be changed for the correct type and the distributor jack shaft is also a different length. An accelerator cable stop and a heater tap or blanking plug will also be required.

The flywheel is drilled to fit a power take-off and is fitted with an 80T starter ring instead of the 102T ring so a donor flywheel and clutch assembly will be required.

At the other end of the engine the oil filler pipe is normally fitted to the timing chain cover and as this will not fit under the radiator header tank it will require changing for the correct type of cover or the filler removed and the blanking plug from the side of the engine fitted. The crankshaft pulley is also different to the car version. A blanking plug is fitted in the location of the car oil filler pipe.

The generator engine dip stick is located on the manifold side of the engine but will probably foul the car manifold and will therefore need to be removed and the hole plugged, and the blanking plug on the other side of the engine punched out to fit the car dip stick. The generator dip stick will not be correctly calibrated.

Whilst on the carburettor side of the engine the tappet cover is different, having no breather holes and a recirculating vent pipe. The oil pressure pipe can be fitted in place of the oil pressure sensor and the oil filter can be fitted in place of the external filtering union. The car manifold and carburettor will replace the generator system. Towards the front of the engine is a large bolt with an extended thread. As this is tapped directly into the main oil gallery it should be left in place unless a blanking plug of the correct thread is available.

At the front of the engine the standard blanking plate is fitted and can be refitted after an inspection of the water chamber for sludge if a water pump is not to be used.

The water jacket is not fitted with a dynamo mounting bracket. It is however an iron casting, unlike the alloy car water jacket which is prone to corrosion, and if there is no sign of leakage it would be wise to leave it in place unless a good alloy casting is available. If fitting the later type of cylinder head a dynamo mounting bracket can be made from dexion or similar and hung from the front cylinder head studs. Depending on whether or not a water pump is to be fitted, the correct inlet pipe/drain tap will be required on the side of the block.

If removing the crankshaft it will be noted that it is different from the unit fitted to the car, having no oil thrower scroll at its rear end, instead having an oil seal. The rear main bearing cap is also different. The correct oil seal will need to be fitted or one made. The crankshafts are not interchangeable between the generator and car engines. As the engine was not fitted to a gearbox it is probable that the drive gear bush into which the front shaft of the gearbox fits will be missing.

What may not be obvious is that the sump is of a different design, visible on the outside by having the drain plug on the left side instead of centrally underneath. Inside the sump has no reservoir casting for the oil pump pick-up. The rear pair of sump bolts are shorter and the baffle plate has no dip stick hole.

The oil pump is a robust looking unit with a filter on the pick-up, however it is designed for static running and suffers from oil pressure loss when cornering in a car. As with the cylinder head, the oil pump may have marine applications.

Car Engine Crankshaft With Scroll

Generator Engine Crankshaft Without Scroll

M. J. Perry

Ammended 01 05 10

Swivel Pin Modification

To convert Series MM cars to Minor 1000 swivel pin assemblies.

This conversion involves a once only modification to the Series MM hub.

The inner bearing is replaced by bearing RHP6205 and the outer bearing by RHP6303. These bearings fit exactly onto the Minor 1000 stub axle. The MM hub then needs machining to take the very slightly larger outer diameters of the new bearings. When machining out the bearing housings care should be taken to machine exactly to the original bearing abutment faces so that the bearings retain their original separation along the stub axle.

 Next obtain a Morris 1000 bearing spacer (distance piece) and have this machined to the same length as the MM spacer by removing metal from the thicker end.

Assemble the hub, bearings, spacer and oil seal normally and pack with grease.

Refit the MM back plate and brakes onto the new swivel pin assembly. Fit the hub assembly onto the stub axle. A steel washer 2-3mm thick with a 17mm (11/16”) diameter  hole will be needed as the 17mm portion of the stub axle may slightly protrude through the centre of the outer bearing. Use Minor 1000 axle nut and split pin. Tighten up as normal.

A word of warning

A previous contributor Tech. Tips has described a different method of converting Series MMs to the use of Minor 1000 swivel pins assemblies. This involves the removal of the larger stub axle and machining the outer portion from 25mm to 7/8” diameter.

This is bad engineering practice. The point of change of diameters is subject to maximum bending moment and the introduction of this stress raiser is likely to cause eventual metal fatigue at this point resulting in the breaking off of the stub axle, so losing the wheel and brakes.

Parts Required

Minor 1000 left and right hand swivel pins and hub nuts

RHP 6205 inner bearings x2

RHP 6303 outer bearings x2

Minor 1000 bearing spacers x2

Steel washers 2-3 mm thick with 17 mm hole x2

How not to do it:  Click HERE

Front Suspension Stub Axle and Wheel Bolt Threads

By Graham Holt

I have studied available written references and practical examples of Swivel pin / stub axle and brake drum assemblies in my possession and the following is my interpretation of ‘what happened when' regarding the various changes carried out on the Hubs, Stub Axles, Hub Retaining Nuts and Wheel Bolts during production of the Series 'MM' and early Series 11 Minors.

I have used the Morris Motors Service Parts List, Issue 3, date Jan 1953,

c / w Supplements 1 to 4 dated Feb 1953 to Aug 1953 as my main information source. I also appreciate the relevant information in Ray Newell’s book 'Original Morris Minor' 

This is a simple version of sequence of changes

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1.         From start of production the Series 'MM' used BSF threads for stub axle retaining nut and wheel bolts.

Stub Axle thread:- 1/2" x 16TPI (BSF).
Castle Nut requires <7/16" Whit/ 1/2" BSF> Socket size.

Wheel Bolt thread:- 7/16" x 18TPI (BSF). Use < 3/8" Whit / 7/16" BSF> Socket size.

1a.       There was a change to the hub and stub axle when a larger outer wheel bearing was introduced (at car no RHD 31790 / LHD 12338 - date c Dec 1949) but the wheel bolts and axle retaining nut remained the same.

This was the set up on my own ‘MM’ car no.69721

2.         Major Change (at car RHD 131858 / LHD 126725 - date c Jan 1952) was the introduction of UNF threads to the Wheel Bolts and larger  axle thread size. Stub Axle thread:- 5/8” x 14TPI (BSF)

Castle Nut requires <1”A/F> Socket size

Wheel Bolt thread:- 7/16” x 20TPI (UNF). Use <5/8”A/F> Socket size

Points worthy of note here are:-

The thread of the Stub Axle/Hub Retaining Nut was changed to 5/8" BSF, but was given a UN Size Hexagonal head. (I believe this may possibly be due to a large qty of stub axles with BSF threads being already available and the Hex Size was introduced to use these up and to meet the requirement of export market, although it meant having a "Special" nut.

The Wheel Retaining Bolts were given the small Hex Head. (Perhaps the Drawing Office had just been introduced to UN fixings and someone didn't check the UN hex size for comparison with BSF hex size ! = just my theory). I believe that the small hex size caused problems in use causing wear in the wheel holes

Perhaps, also, the smaller hex size made the different bolt more distinguishable.

The rear axle hubs, the spare wheel retaining clamp bolt and the wheel brace / hubcap lever supplied with each car, were also amended to suit, at this time.

This was the set-up on the 'MM' which I stripped for spares in 1976 - Car No 173726. I can confirm that the rear axle and wheel bolt details agree with the above. I believe that the car was quite original. (I did not acquire the front hubs though!).

I regret that my available information does not include much on the early Series II, for comparison. I note that Ray Newell‘s book does say that the wheel bolt was given a larger hex size in March 1953 at car no 184760,  after 'MM' production had ceased.
Size quoted is 0.705" / 0.710" A/F, which equates to a 3/8”Whit / 7/16”BSF Hex size !!!! So I presume that early Series 11's went back to same size as early Series 'MM's

 Additional Notes by Michael Perry

3.         “Minor 1000” Suspension introduced on the Series II Traveller, car no. 216901. Swivel Pins distinguished by blank circular boss above steering arm.

  Axle thread is 5/8” x 18TPI (UNF), usually written as 5/8 - 18 UNF)

Castle Nut requires 15/16” A/F Socket size

 Wheel bolts were changed to wheel nuts.

Thread:- 3/8” x 24TPI (UNF), use 3/8”Whit / 7/16”BSF Socket size

 There is a set of instructions in Tech. Info for converting Series MM brake drums to fit M1000 swivel pins

 I would recommend that the thread detail (i.e.:- external diameter and TPI = threads per inch) are checked for every enquiry because early Minors had a number of “versions on a theme” as regards axle threads  as well as axle lengths.

And anything may have been fitted to any car of any year as a ‘get out of trouble’ quick fix during it’s life time, only to cause problems years later

Especially do not trust the hex size of any bolt to define it’s thread.

Table of appropriate axle thread sizes

(a) ½”   BSF = 16TPI           

(b) 5/8” BSF = 14TPI

(c)  ½”    UNF = 20TPI (½ - 20 UNF)

(d) ½”   UNC = 13TPI (½ - 13 UNC)

(e) 5/8” UNF = 18 TPI (5/8 - 18 UNF)

(f)  5/8” UNC = 11TPI (5/8 - 11 UNC)

 This information is extracted from “Zeus Data Chart and Reference Tables”               
Graham Holt.

Combined Indicator and Trafficator Wiring Diagram - CLICK HERE