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  1. #1
    JeffC
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    M5 engine rebuild project

    Hi guys,

    Looking for other folks's pictures or experience who have rebuild an M5 to ease our process.

    I now own my buddy's 1991 M5 who is running rough (cant see it being parted), besides the engine, everything else is impecable, exactly what I wanted. It was running well until he left it run lean for too long (bad intake boot).
    This should be a fun project as I always wanted to take one apart and see how it all works.

    We did a compression test and it does not look good.
    Cylinder #1 150psi, #2 160, #3 140, #4 130, #5 80, #6 100. shot some oil into 5 and 6 and we got #5 100, #6 150PSI. Seems like 5 might also need some valves based on our diagnosis.

    So the head is coming off this weekend, and we are probably going to need pistons and rings. Should not be very different from the 535 we rebuild a year ago.

    Does anyone know have experience this before and can share some experience on this and also provide some feedback on which piston we should be ordering - 93,355MM("0"), or 93,405MM("00") if the cylinder is in good condition and we do not need to rebore

    Has anyone changed all their pistons previously and would sell/send us the older good ones or have a couple from a set that they did not use.

    We though we should play around with it for a while before order custom pistons with thermal top coat and low friction side skirt plating.

    Thanks
    Jeff

  2. #2
    JeffC
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    what is a good hot and cold compression numbers

    Any one know what a good number is? along with the spread across the cylinders.
    Thanks

  3. #3
    JeffC
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    Anyone with a set of pistons after an upgrade

    Anyone out there who has done a perf upgrade and have the old pistons and rings sitting around and want to let it go?

    Let us know
    Thanks

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