  We have made an asteroseismic analysis of the variable blue stragglers in the
open cluster M67. The data set consists of photometric time series from eight
sites using nine 0.6-2.1 meter telescopes with a time baseline of 43 days. In
two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41
and 26) detected in delta Scuti stars belonging to a stellar cluster, and EW
Cnc has the second highest number of frequencies detected in any delta Scuti
star. We have computed a grid of pulsation models that take the effects of
rotation into account. The distribution of observed and theoretical frequencies
show that in a wide frequency range a significant fraction of the radial and
non-radial low-degree modes are excited to detectable amplitudes. Despite the
large number of observed frequencies we cannot constrain the fundamental
parameters of the stars. To make progress we need to identify the degrees of
some of the modes either from multi-colour photometry or spectroscopy.
