By the way, did you try what Daniel was leading towards?
to3d -prefix test.hdr -time:zt 31 4 2800 alt+z S40vol.4.hdr
Note that if your S40vol.4.hdr dataset has the correct 4-D
info (including timing information), then you don't even
need to use to3d. i.e. if you have overwritten the .img
with the data you want to use, that is enough.
But if you want to fix the timing info in S40vol.4.hdr, then
the above 'to3d' command would do the trick (say if the slice
timing was not in the original dataset).
If you provide more details, maybe we could be more helpful.
- daniel & rick