After all the probs with the valve train on Col's 3dr we made an interesting discovery that i thought fellow zetec builders might appreciate knowing.

Not all zetec valve springs are equal!

The later black top focus engine has tapered valve springs with different caps. The were designed to be easier to open and therefore increase economy though reducing valve train losses.
The down side is that in a performance situation they are shite! Adsolutly no good for anything over 6.5k. Early zetec E valve springs are the ones to use as they are good for 7.5k. You can feel the difference between the two by squeezing them between your fingers.