The Briton said the FW27 has improved at every race since Melbourne, even if it didn't show.
"This is partly down to our not too impressive starts," Head explained, "which often caused slower cars to get in front."
Williams' impressive German driver Nick Heidfeld reckons the BMW-powered car will be ready to win 'on merit' in the approaching second half of 2005.
That, the 28-year-old urged, would be the best way to convince Williams - or BMW, should the case be - that he is worth signing for another year.
Heidfeld said of Frank Williams' Grove based team: "A lot of people told me that the atmosphere at Williams is cold, that the management is extremely rigid. None of it is correct."