The conformal algebra of a 1+3 decomposable spacetime can be computed from
the conformal Killing vectors (CKV) of the 3-space. It is shown that the
general form of such a 3-CKV is the sum of a gradient CKV and a Killing or
homothetic 3-vector. It is proved that spaces of constant curvature always
admit such conformal Killing vectors. As an example, the complete conformal
algebra of a G\"odel-type spacetime is computed. Finally it is shown that this
method can be extended to compute the conformal algebra of more general
non-decomposable spacetimes.Comment: 15 pages Latex, no figures. Minor mistakes correcte