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Thread: 20 valve pushing oil from valve cover breather after rebuild

  1. #1
    Junior Member 1st year Apprentice boon280's Avatar
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    Default 20 valve pushing oil from valve cover breather after rebuild

    I have just put a set of rings and bearings in my silvertop and now it is breathing oil from the valve cover under high revs and load.
    Is there anything that i could look for before pulling the engine apart?
    I think that maybe the rings did not bed in properly.
    The engine is being used for offroad racing so it is under high revs and load constantly.
    any ideas would be appreciated.

  2. #2
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    My guess is your block and head and under pressure and the only thing that i guess can cause that is air getting past the piston rings, or your valves maybe. unless your running some sort of forced induction.....

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    Junior Member 1st year Apprentice boon280's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    no forced induction all standard engine and ecu

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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    Test your compression let me know your figures..

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    ......... Carport Converter jeffro ra28's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    leakdown and compression test first and formost.

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    Junior Member 1st year Apprentice boon280's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    ok will try and do tomorrow night

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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    excellent let me know what happens i need rep points. hehehehe

  8. #8
    Junior Member Backyard Mechanic
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    Check that the engine breather tube (most likely going from the rocker cover to somewhere into the inlet manifold) is not blocked.

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    Junior Member Carport Converter StuC's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    and not just the tube but the PCV (positive crankcase breather) its basically a 1-way valve for blowby

  10. #10
    Junior Member Automotive Encyclopaedia
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    did you dunny brush the bores before you put the new rings in with kero ,or just put said rings in and hope they might bed in ,if bore is glazed your out of luck ,pull head off and strip bottom end and deglaze bores and then put the same rings back in

  11. #11
    Junior Member 1st year Apprentice boon280's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    did a compression test tonight and have pressure readings from 200 to 220 psi .is this too high? as I fitted a non genuine head gasket that is thinner than the standard one, seems to have excessive blow by on number 4. block was cleaned thoroughly before re-assembling.

  12. #12
    Junior Member Automotive Encyclopaedia
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    was it rehoned with a dunny brush thou

  13. #13
    Junior Member 1st year Apprentice boon280's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    yes it was honed with a "dunny brush" (sorry I just got what you meant)

  14. #14
    Junior Member Backyard Mechanic
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    Excessive blowby on one cylinder might mean a broken ring. Did you use a ring compressor?

  15. #15
    Junior Member 1st year Apprentice boon280's Avatar
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    Default Re: 20 valve pushing oil from valve cover breather after rebuild

    yes a ring compressor was used, the motor was assembled by a good friend of mine who is a qualified mechanic and has done many engine rebuilds.

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