The valence level hole spectral functions of linear C2n+1 (n=1–6) clusters are calculated by the ab initio third order algebraic diagrammatic construction [ADC(3)] Green function method and the outer-valence Green function (OVGF) method using an extended basis set. The vertical electron affinities of linear C2n+1 (n=1–6) clusters are also evaluated by the same methods. With an increase of the number of carbon atoms, the KT energy levels become more closely spaced and start to form quasi-continua. The original spectral strength of the main line becomes distributed over several lines of comparable intensity. With an increase of the number of carbon atoms, the one-electron (or even quasi-particle) picture of the ionization breaks down because of the interaction between the initial single hole level and the final two-hole-one-particle levels. The spectral intensity of the first four ionization levels remains fairly constant independent of the number of carbon atoms. The agreement of the affinities of C2n+1 (n=1–6) with experiment is in general very good. Two anionic states are found to be bound for C9, C11 and C13.