Series MM coil

[Mr Spigot]

The coil on my 1952 MM looks to be the original one and while it works perfectly, I wanted to carry a spare in case the inevitable happens. The car has the original 918 sidevalve engine and distributor. There are reproduction 'Q12' coils available for around £80, but I wondered if a simple 12v coil for around £20 would suffice. What are the options? Does the same coil work for all versions of the Morris Minor?

[myoldjalopy]

The Q12 coil used on the MM models was, apparently, also used on the earlier SII cars. It was later replaced by the LA12 coil, which was then used on all future models of the car, so I would say the same coil should work on all models. A 'simple 12v coil for around £20' should be OK, but I wonder about its longevity. reputation.Modern, cheap coils don't seem to have a good reputation. A better bet might be a good, old coil picked up from an autojumble.

[geoberni]

I can't find a part number for a MM/918 Coil, but there were certainly quite a few different part numbers used during the full production run.

Checking the Car & LCV Lists for all 803/948/1098 engines, they used a Screw Top Coil until sometime into the 1098 engines at 10MA/U/H/215530 and /L/215634 .
If your Coil is still a screw top, then your choice is a little limited, although Accuspark do one for £20, the other makes seem to be £40.
But you can always make up a HT Cable with a push fit and keep it with the spare coil.

So long as it's a12 Coil it'll work.
Early Coils were a bit smaller diameter than the later ones, so that's something to check for fit.

[Mr Spigot]

Thanks for the information. I have a good secondhand original Lucas 'Q12' type, tested and working, which I shall keep as a permanent replacement if needed. The original part number looks to be 45020B. I shall get a cheap 12v one to keep in the boot if required as an emergency 'get-me-home' job.

[MM1949]

One thing to consider is that the series MM coil is mounted on the bulkhead pointing downward and is not oil filled, so an oil filled later spare coil in that position may fail quite quickly.

[geoberni]

One thing to consider is that the series MM coil is mounted on the bulkhead pointing downward and is not oil filled, so an oil filled later spare coil in that position may fail quite quickly.

Shouldn't do.
My SII has the Coil on the bulkhead with no ill effects. With the build quality of modern coils, it's better there than being subject to the vibration of sitting on the engine.

I didn't realise the MM Coils were not oil filled. I assume they were bitumen filled then?
I've seen reference to that in old Lucas documents in general terms, e.g. 'early coils were filled with bitumen, more recently they are oil filled' but no reference to when the document is written.
I've seen glass jar oil filled coils from the 1930s, so oil filling was around very early on.

Oil filled coils only have a small space in them to allow for expansion of the oil as it heats up, otherwise the expanding heated oil could split the casing.

[myoldjalopy]

Yes, my SII has the later LA12 coil mounted on the bulkhead and it has been no problem whatsoever in that position.