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Thread: is it un-advisable to spin an engine backwards?

  1. #1
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    Default is it un-advisable to spin an engine backwards?

    I'm certainly not talking about spinning it over backwards with a reversed starter motor or anything like that, more along the lines of lining up torque converter bolts, adjusting valve trains, et cetera. I've heard this advice for the second time last weekend, with the explanation that in timing belt driven cars, one does not want to reverse the tension while under load. can anyone clarify or dispel the advice i received? thanks.
    "..Torchinski v. Peterson that it is legal to carry a concealed weapon, so long the weapon is totally slick like a huge ass machine gun that you carry under a trench coat, like in the Matrix."


  2. #2
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    I see no harm. Done it myself coutless times with no ill effect.
    EDit; Lots of good reasons given here not to do so. I'll consider myself lucky so far or to have had healthy timing gear.
    Last edited by Ross; 01-07-2009 at 12:51 PM.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  3. #3
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    Dont think it matters. But I wouldnt line up my timing marks turning the engine backwards. Why? Think Bill R put it best when he quoted his dad:
    ' cos I said so'

  4. #4
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    only thing I would avoid reversing it would be in setting timing.
    95 E34 530I V2.37
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  5. #5
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    Can be very bad if your tensioner is weak.

    the tiiming chain will slacken and skip a tooth or two.


    Vee ave vays of dealing vid your kind...........

  6. #6
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    now that would suck!
    Quote Originally Posted by Blitzkrieg Bob View Post
    Can be very bad if your tensioner is weak.

    the tiiming chain will slacken and skip a tooth or two.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  7. #7
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    Turned my M50 backwards plenty. Can't see how one could bugger anything up turning it by hand. However, your question mentioned timing belts, not chains. There might be truth in not wanting to turn a belt backwards, but I dunno................

    Dave

    10/90 Build 525im, 630,000+km, Eibach/Sachs, Engine Rebuild
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  8. #8
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    Quote Originally Posted by Blitzkrieg Bob View Post
    Can be very bad if your tensioner is weak.

    the tiiming chain will slacken and skip a tooth or two.
    +1, big time.

    Doing so on a clutch job has taken out S38's before. Will have to look up the last thread on this happening on the M5board. Poor guy took his E34 M5 in for a clutch job and blew up his engine because the timing chain jumped a tooth or two and the pistons hit the valves. The pics weren't pretty.
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  9. #9
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    Cosmos Black/Black 1995 540iA M-Sport
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  10. #10
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    Default The advice you received is accurate,

    you don't want to turn a timing belt equipped car backward or for that matter any timing chain equipped car that has a tensioner. They can jump a tooth and in the case of a chain bunch up or break a tensioner or guide rail. Sometimes it unavoidable but you want to avoid it whenever possible.


    Quote Originally Posted by ryan roopnarine View Post
    I'm certainly not talking about spinning it over backwards with a reversed starter motor or anything like that, more along the lines of lining up torque converter bolts, adjusting valve trains, et cetera. I've heard this advice for the second time last weekend, with the explanation that in timing belt driven cars, one does not want to reverse the tension while under load. can anyone clarify or dispel the advice i received? thanks.


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