\ensuremath{\beta}-delayed proton decays of the nuclides $^{27}\mathrm{P}$ and $^{31}\mathrm{Cl}$ were measured using the helium-jet recoil collection technique and low-energy particle identification detector telescopes. In $^{27}\mathrm{P}$, two new proton groups at 466\ifmmode\pm\else\textpm\fi{}3 keV and 612\ifmmode\pm\else\textpm\fi{}2 keV, with intensities of 9\ifmmode\pm\else\textpm\fi{}2% and 97\ifmmode\pm\else\textpm\fi{}3% relative to the main (100%) group at 731\ifmmode\pm\else\textpm\fi{}2 keV, were discovered. Additionally, during the $^{27}\mathrm{P}$ experiments, a new proton transition was identified following the \ensuremath{\beta} decay of $^{28}\mathrm{P}$. This group, at a proton energy of 1452\ifmmode\pm\else\textpm\fi{}4 keV, had a 2\ifmmode\pm\else\textpm\fi{}1% intensity relative to the 100% group at 679\ifmmode\pm\else\textpm\fi{}1 keV. A total $^{27}\mathrm{P}$ \ensuremath{\beta}-delayed proton branch of 0.07% was estimated. The experimental Gamow-Teller \ensuremath{\beta}-decay strengths of the observed transitions from $^{27}\mathrm{P}$ were compared to results from shell model calculations. A search for new proton transitions in $^{31}\mathrm{Cl}$, the next member of this A=4n+3, ${\mathit{T}}_{\mathit{z}}$=-3/2 series, was unsuccessful. However, several proton peaks that had been previously assigned to $^{31}\mathrm{Cl}$ decay were shown to be from the decay of $^{25}\mathrm{Si}$. \textcopyright{} 1996 The American Physical Society.