By using noninteger n-Slater type orbitals in combined Hartree–Fock–Roothaan method, self-consistent field calculations of orbital and lowest states energies have been performed for the isoelectronic series of open shell systems $K[Ar]4s^0 3d^1 ({}^2D) (Z = 19–30)$ and $Cr^+[Ar]4s^0 3d^5 ({}^6 S) (Z = 24–30)$. The results of the calculations for the orbital and total energies obtained by using minimal basis-sets of noninteger 𝑛-Slater type orbitals are given in the tables. The results are compared with the extended-basis Hartree–Fock computations. The orbital and total energies are in good agreement with those presented in the literature. The results can be useful in the study of various properties of heavy atomic systems when the combined Hartree–Fock–Roothaan approach is employed.