Is it possible to have a dilated LV but normal EF?

Probably somewhat unlikely, but I would look askance at a claim that it is 'impossible'. Remember, too, that there is a range in both 'normal' for ventricular size AND FOR ejection fraction. Strictly speaking, from a statistical standpoint, any number within one standard deviation above and below the 'mean' lies in the range of 'normal' or 'average.' That's quite a spread. I honestly don't know if the curve is non-standard for these measures, but I'm pretty sure the answer to your question is, 'Yes, quite possibly'.