How To: Tell the difference between Mini A Series / A + Engines

Distributors between the A Series and A+ engines are not interchangeable.

The A Series Engine uses a 45D or 25D Distributor

The A+ Engine uses a 59D or 65D Distributor

Mini A Series Distributors (up to 1980) are held in place by a pinch clamp and 2 bolts.

Mini A Series Clamp

Mini A + Distributors are held in place by a Y clamp and a single bolt.

Mini A+ Clamp

To identify the difference between these two engines, read on…!

Much has been written about the A Series engine, and one of the best articles is this one written by AROnline founder Keith Adams. It’s a great place to read more detail about the ins and outs of the A Series engine and it’s history and development.

The A+ engine came on to the mini scene in 1983. It has a thicker block to box flange and is generally more robust than the standard A series. Operationally it’s pretty much identical and is the same capacity. Heads/boxes are swappable.

Here are the A+ distinguishing features:

• Strengthening ribs on the back of the block at the clutch end
• Thicker block-gearbox flange
• Dizzy clamp is a forked plate with a single bolt into the block
• Dipstick sits directly in block, not in a tube, and is shorter
• Verto clutch, slave on plate slanting downwards, short arm. (NOTE: The very first A+ engines had a pre-verto clutch)
• Alternator bracket mounting holes are closer to the rad on the A block
• ‘A+’ stickers on rocker cover if a Metro!

NOTE: The 1275 crank fouls the inside of the gearbox casting on earlier 1960s unless the ‘box came off an “S” originally.

They standardised in ’68 or ’69. The changeover to A+ didn’t occur on all parts at once. Some engines had eg: A+ block and pre-verto clutch, and some had A block/box and A+ bits bolted on. Maybe BL running down stock.

One correspondent has an A+ engine as described above, but it was the original engine from a 1981 New Zealand model 1275GT. It does not have a verto clutch, but the gearbox is the A+ type, and so is the block. It could have just been a test by Austin-Rover to see if their engine was any good before it was released in the UK in 1983.

It is possible to put an A series engine onto an A+ gearbox and vice versa, but the transfer housing and drop gears *MUST* be the same type as the gearbox, as the idler bearings are different sizes. Apart from that nothing to it.

Home brew Engine Decoder shows weather you have A series or A+

A Series and A+ Distributor Drive differences:

12 thoughts on “How To: Tell the difference between Mini A Series / A + Engines”

    1. There are a few ways to note the type of engine if that is what you mean and we can help you with that but the two will more than likely not weigh the same but I do not have specifics and it certainly isn’t anything we have compared.

  1. That’s very interesting thanks.
    I have a 1980 sure it has a+ block and gearbox.
    I will have a look.
    Many thanks Chris
    Dont suppose any slipped out with bigger valve heads on,?😂

      1. Thanks for the reply.
        I will keep you updated.
        I got the car when it was only 4 years old and has been in my family ever since so it’s unlikely to have ever had anything swapped pretty sure this car is how it came out of the factory.
        I will be taking the head off soon.
        I had a look in the rocker cover over the weekend and it does have the sintered type rockers in it.
        Thanks for your time and input.

  2. On the 25d distributor where should the mechanical advance ,the mirco wheel be set to, when timing up the engine as there are no markings on this like the original lucus item.

  3. I have just obtained an A+ motor to fit into my 1968 Mini and purchased a PowerSpark distributor 65DM4 to fit. I already have converted to negative to earth and alternator on the car.

    My question is what are the three wires from the dizzy to be connected to? My current setup has only two.
    Am I right in thinking one to the “+” and “-” of the coil and the other back to the ignition? If so which terminal is which (looking down from the top with the module closest to me)? There are no colour markings for the terminals.
    Thank you

    1. It is only the two wires that are needed in reality with the + going to the coil + and the – to the coil -. Provided you have a good earth this will function just fine with that.
      Let me know how you get on, we have link leads in stock should you want to terminate from the module easier?
      Please call 01527 889 453 for any further help.

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