This paper reports observations of six out of 42 interstellar molecular cloud cores identified by the CS survey of L1630 by Lada, Bally & Stark. High-resolution ( arcsec) maps in J=3→3, 4→3 HCO+ and 5→4 CS identify at least 22 emission maxima, 14 of which are associated with two of the former cores. Lower resolution (60 arcsec) maps of the J= HCO+ emission show little or no evidence for the structure seen in the higher-J maps. Three of the six cores are significantly elongated - we conclude that they are probably filaments rather than fragmented discs or rings seen edge-on.Most of the maxima are unresolved in a arcsec beam; therefore most of the virial mass estimates are upper limits. Those that are not suggest clump masses of a few Msun. Masses derived from dust continuum observations in one of the cores (number 23) are in good agreement with the virial masses. LVG analysis has been applied to a two-component model of the cores in which the 1→0 HCO+ emission traces a low-density (104 cm-3) envelope while the3→2 and 4→3 and HCO+ lines trace the higher-density clumps (106 cm-3). These clumps are excellent candidates for low-mass protostellar activity.