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Discussion in 'E31 (1991-1997)' started by Solrider726, Jun 24, 2008.

    Solrider726 guest

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    I just had a simple question to end a debate with a friend. Is the S70B56 engine found in the 850 CSi made of all aluminum, iron and aluminum, or all iron?

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    Hi Solrider726:
    I posed your question to Jud Spencer, the 8 series registrar and fountainhead of knowledge on all things E31 related ...

    The aluminum answer is closest to being correct, although the block is actually a light metal alloy of aluminum and silicium (according to the S70 engine BMW technician training manual).

    It is not 100% aluminum (the ratio Al/Si is described as 83/17 for the original M70 version of the V-12).

    Hope this helps ...

    (Thanks, Jud, for the copies of the BMW documents).

    Mark in mid-MO
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    • Technical Service Advisor


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    No blocks are 100% aluminum, because it is too soft. Nearly everything on your car that is aluminum is actually an aluminum alloy. So this is simply an aluminum alloy block, like all other aluminum alloy blocks (all of varying compositions.)

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