MU3485

[Francis Sanders]

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MU was my father’s car, which I inherited. It resided in Oxfordshire until I moved it to Newport, South Wales in March 2023.

I’ve included a couple of photos of MU in situ at the new residence.

Currently issues noted in the last 200 miles of running since the move:
- starter not working - related to this I sheered the starter handle but have repaired this with a somewhat bodged job of an old impact driver bit which fits quite nicely. I have also had to leave the front engine mounting bolts slightly loose to get the starter handle correctly seated to start - I suspect I need a couple more spacer washers or equivalent underneath to hitch the engine up a little.
- occasionally tricky getting into 2nd gear on the way up the box - have to give the gear knob a slight tilt and twist anticlockwise and it’ll eventually sort itself out
- distributor cap from the magneto is live (found that out the hard way)
- horn appears faulty
- obligatory squeaky brakes

It would be great to have advice on standard stuff: oil, filter, spark plugs, battery etc. to do a basic service on her since her time off the road.

Other than that she runs wonderfully when she’s going. Any thoughts or comments very welcome.

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[Ian Grace]

Hi Frank, and welcome to the forum.

Re the front engine mounts, it sounds like perhaps the rubber bushes under the engine bearer have compressed - a common problem solved with new bushes.

I've had starter problems in the past, which were never the fault of the starter motor, but a poor earth return from the engine to the chassis and back to the battery. The engine sits on rubber, which does nothing for conduction. You can help this enormously by adding a stout earthing strap from the engine to the chassis. Try something temporary to see if it makes a difference first.

Regarding oil filtering, a couple of suggestions. First, always make sure that the large screw cap on the external oil filter is TIGHT. If it is loose, or there is the slightest crack, it will suck in air which will be ruinous to the bearings. I would also check the gauze filter inside for any holes. if you find any, clean it thoroughly and use solder to patch the hole I would also recommend popping a rare earth magnet into the filter to collect any small steel fragments and check it occasionally. (You can also attach other rare earth magnets to the gearbox and diff. drain plugs.)

Just a couple of thoughts for starters. Others may have more to contribute.

[Ian Grace]

Another thought. While servicing, drain the gearbox and put in straight 140 gear oil. It does make a big difference and makes gear changing easier. Use the same in the back axle, but don't fill the axle up to the brim of the filler hole. It is unnecessary, and too high an oil level will encourage oil to exit to the hubs, and then the brake linings. You just need to be confident that the crown wheel is dipping into the oil.

Do you also have your father's Bentley with you?

[Ian Grace]

So your fabric saloon is a 1931 season model (chassis M32249) and as such has the 'leather grain' steel bonnet which was also fitted to the fabric-bodied 2-seater which was only produced for the 1931 season. All the earlier fabric saloons had plain bonnets, like the steel saloons, tourers and vans.

By 1931, fabric bodies were rapidly falling out of vogue and so yours is a rare survivor. Only three other 1931 season fabric saloons appear on the Chassis Register.

A fabric bodied SV Minor was introduced in 1931, but sadly, no survivor is known. I suspect that these would also have had the grained bonnet.

These bonnets always make a great talking point at pub meets!

Oh, and just to be a complete anorak, the 'MORRIS' script on the radiator core was only originally fitted to the first season's cars - 1929. It is believed this was added by Morris to distinguish the new cars from Austin Sevens which were ubiquitous at the time, but it was dropped for the 1930 season Minors.

[Francis Sanders]

Ian - thanks for all the information. Very interesting to know the background of the 1931 minor saloons. I’m more sure I’ll remove the morris type off the radiator just yet - annoyingly I quite like how it looks. Very superficial of me!

I’ll try and source some rubber bushings and a rare earth magnet in the filter. I definitely already have a candidate as an earth candidate for the cable so that’s grand.

What grade oil do you tend to use? I use 10w40 pistoneze on the old bike or valvolene VR1.

Thanks again for the help

Frank

[Ian Grace]

I'm old fashioned and use Straight 30, but I know others use 20/50. Just avoid Hypoid oils which eat any bronze in the bearings.

[Francis Sanders]

Thanks for all this help Ian. I’ve been running her around a bit and just changed the oil again. The spark plugs were also fouled so I have changed them - I’ve changed them to NGK AB6 (some very elderly A6s were in there).

The next bit of routine maintenance I wanted to check was the cam follower adjustment - how do you do this as I cannot figure it out from previous cars I’ve worked on? And I haven’t been able to track anything down on the forum

Thanks again

[Ian Grace]

Aha! This adjustment gets to the core of the OHC cylinder head design!

Basically, you adjust the geometry of the rocker fingers to adjust the gap between the finger's working surface and the end of the valve stem. You do this by adjusting the rotary orientation of the eccentric bronze bush that mounts the finger to the rocker shaft. This is done by loosening the thin hex nut that clamps the bronze bush into the finger. You should get a pair of spanners of the right size (can't recall from memory) and grind their sides down to make them thin enough to fit on the nut and the hex on the eccentric bush.

The original spanners were about 1/8" thick and I have an original which I was going to user as a pattern to have a batch laser cut, but there was scant interest. Now I'm back in England, I might resurrect the project anyway.

There is another method of adjusting the rocker fingers that is a great deal more work, but does get around a slight flaw in the above procedure. The flaw is that, as you rotate the eccentric bush to achieve the requisite clearance, then the position of the point of contact between finger and cam lobe moves, so the valve timing moves with it. The second method is best used when setting up a head before fitting it. Set all eight of the bushes in exactly the same orientation and then grins some metal off the ends of the valve stems and fit hardened steel caps. Now you can grind the caps to achieve the gaps, so the gaps are all correct and the valve timing isn't compromised. A ton of work, and probably only worth it if you want the last ounce of performance!

One more point. New Minor/M Type rocker fingers are not available, but J2 fingers are, and can be used on Minors and M Types. Their design does away with the hex on the bush and the locknut by having a split finger, secured on the bush by a clamp bolt and nut. The only problem when fitting these to Minors is that the clamp bolt head just hits the steel rocker cover, but you can grind a little metal off them to avoid this. (I don't think this is a problem with the alloy rocker cover on the M Type.)

The good thing about using these new J2 fingers is that the profiles of the two working surfaces are exactly correct. So many original Minor fingers are either worn to the point of compromising the timing but have been welded up and had the working surfaces re-ground to profiles that might not be absolutely correct. I small error in the profile translates to a significant timing error.

[Francis Sanders]

Okay this makes a lot of sense - I wondered if it might be something along those lines. Quite a fiddle really compared to tappets on a push rod.

But I may give it a try next summer - I don’t have any great concerns and I need to fix my starting handle anyway to turn over the engine with ease - best get that sorted first anyway. Unfortunately the spigot sheared off so I have machined a replacement from some unidentified spare steel from my friends coach yard and need to tack it in place.

[Ian Grace]

Frank, you also mentioned in your e-mail that the car suffers from very squeaky brakes. This is very common with Minors - particularly the OHC cars that had the early type of small-flange brake drum. These drums were stamped out of sheet steel somehow and are quite thin, so they are very prone to ringing like a bell under braking.

There are a couple of thing you can try. First, you can fit anti-squeak bands. These were fitted to some Minors at the factory - perhaps because of squeaky brakes during gtheir final road test. We know this because I have a high resolution Morris promotional image of the Semi-sports prototype and the bands are clearly visible. Basically, it is a steel band that clamps around the drum and is fitted over a strip of rubber. Original bands can sometime be found or you can fettle something up yourself, or I have seen large Jubilee clips used.

Another fix is to fit later-type SV Minor brake drums, which were cast and are thicker and therefore more substantial and less prone to distortion under braking. These have a wider flange, so don't fit inside the early brake backplates, but you can easily machine them down.

I have just had a set of SV drums machined for my 1929 tourer which I am about to fit.

[Ian Grace]

However, note that the stronger brake drums were introduced at chassis M29528:

From the website:

"M29528 Transmission handbrake replaced by cross-shaft operated wheel brakes. Front brake cables re-routed to brake lever forward of wheel hub with shackled pulley on top of kingpin. More angled brake cam levers introduced. Wider rimmed brake drums/backplates fitted"

(https://www.vintageminor.co.uk/tech/index.htm)

Your car is a very late fabric saloon, with chassis number M32249, so you should take a quick look at your brake drums to see if they are narrow or wide flange. Also, does your car have a transmission handbrake behind the gearbox and are the front brake cable connected to levers on the backplates forward or aft of the axle beam?

(Sometimes, the chassis numbers associated with design updates can be a bit suspect, as the factory tended to use up existing parts stock before making the called-for changes.