As posted 200bhp is the cut off point for easy tuning of the Zetec FOCUS BLACK TOP, to tune to this level its cams,throttle bodies and if your keen a bit of a head tidy up and have the stock flywheel lightened.
To take things further you run into valve piston clearance problems that prevent you from running hotter cams, it is possible to have the pistons pocketed run hotter cams and get 220 bhp with some head work but probably not an economic route over fitting forged pistons as the stock compression ratio is too low for power. The next stage to get up to 250 bhp requires some extensive porting of the head,machining of the head to fit larger cam followers,increased valve sizes, steel con rods,forged pistons, hotter cams,comp valve springs& steel retainers, full engine balance, etc etc in short a full competition engine. On the positive side the engine does not need drysumping the Raceline wet sump copes well on track even in race conditions using slicks.
It is unfortunate that the Zetec has never been really developed by the tuners, Possibly the engines lack of potential to compete on power terms with the VX redtop on ultimate power terms and the difficulties faced to tune past 200bhp have seen it past by which I think is a shame as its a good strong engine.
I would look into supercharging the engine and consider forced induction through the throttle bodies having first passed through the biggest charge cooler I could fit into the car, stick with the wet sump. A budget of 5K should acheive some usefull grunt.
Rob
Edited by - Rob Walker on 19 Jan 2013 18:49:38