The zetec engine cannot reliably make beyond 400bhp without considerable work to the cylinder head as the exhaust ports are very restrictive! As standard the head has smaller exhaust ports than a Cosworth YB and 3mm SMALLER valves!
To achieve a 450bhp engine, the bottom end is rebuilt as in the 400bhp engine, but in addition we now use NMS designed Farndon H section con-rods and Mahle motorsport pistons with a lower compression ratio.
The cylinder head is comprehensively re-worked, enlarging the inlet ports to 25.5mm and the exhaust ports to 24.5mm. This is the practical maximum if you want a reliable head without being VERY close to breaking through to the water jackets! Standard valves are refaced and refurbished, multi angle valve seats to optimise the standard valve size. The valve springs and retainers are changed to uprated items, and a pair of NMS high lift, longer duration cams and verniers are fitted using the standard followers, and reshimmed to suit.
The block and head are modified to accept our M12 head bolt conversion and an uprated MLS head gasket is used.
The inlet manifold is changed to either an aluminium HO item or one of our custom centre entry large plenum items, and fitted with our large bore thick wall tubular manifold, a Garrett GT30r and external wastegate. Maximum safe rpm of 7500rpm.