Pin drive oil pumps and S pistons


  1. Hi,

    Does anyone know if the Cooper S pin drive pump is available anywhere? They have a different length (shorter?) shaft. I have heard that some repro pin drive ones sheared the drive too?

    I also need some +10 'S' pistons – anyone know of any around? BMC used to make them I think



  2. imported post

    Hi Graeme,

    The S pin drive pump has a longer shaft and as far as I know is not available anywhere. It wasn't when I was trying to get one for my S engine. However, it is possible to press the shaft off the old S pump (fitted on a keyway) and fit it to a new high capacity oil pump (denoted by the shoulder on the pump housing) intended for a small bore engine. Justtake careful measurements to make sure the pin is correctly positioned on the rotor.

    Hope this helps


  3. imported post

    Swaping the pin is the only way to go on an old S pump, or even better stick a more modern cam in it and use a modern pump 🙂

    I have never heard of a 10thou oversize piston, the first rebore size is 20thou.


  4. imported post


    Thanks to for that about the oil pumps.

    Oversize +10 pistons are listed in my mid 1970's parts book – 8G 2434 13 for the set of four Grade 3 . Also listed as 8G 2434 16 as Grade 6. (I think the grade 6 pistons were slightly larger for slightly worn bores)

    They are also listed for the 970 – these must be flat tops. These are also listed in the Australian S/T booklet (link below) in the S/T section of that terrific website!


    I too have never seen this size piston but have an old thin flange S block that has fairly thin liners and has been bored to +10. I didn't really want to risk boring it out to +20.

    Cheers, Graeme

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    +50 pistonsalso used to be available in the good old days when we had a choice not that I can recall having seen an S piston in either of these sizes.

    Even old liners should be able to go to +30.

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