\version "2.18.2"
% => http://lilypond-french-users.1298960.n2.nabble.com/Portee-a-huit-lignes-deux-clefs-et-deux-bemols-tt7581415.html

global = {
  \time 4/4
  \key d\minor
}

high = \relative c' { c1 }

low = \relative c' { f1 }

\new StaffGroup 
\with { 
  \override StaffGrouper.staffgroup-staff-spacing.basic-distance = #11
  \override Clef.font-size = #-4
  systemStartDelimiter = #'SystemStartBar 
}
<<
  \new Staff = "High" 
  \with {
    clefGlyph = #"clefs.C"
    clefPosition = #-3
    middleCPosition = #-3
    middleCClefPosition = #-3
    \override StaffSymbol.line-count = #4
    \override VerticalAxisGroup.staff-staff-spacing = #'((padding . -.5))
    \override TimeSignature.extra-offset = #'(0 . -2)
  }
  { 
    \global
    \high
  }
  \new Staff = "Low" 
  \with {
    clefGlyph = #"clefs.F"
    clefPosition = #1
    middleCPosition = #-2
    middleCClefPosition = #-2
    \override StaffSymbol.line-count = #4
    \omit TimeSignature
  }
  {
    \global
    \low
  }
>>