Series 1 Zetec-E - 1993The first production Zetec dates back to 1992, when it first appeared in Escorts (1.6 and 1.8 )Fiestas (1.8 ). The 16v head was developed by Yamaha and based on a redesigned CVH block. The Mondeo was the only vehiclele to use the 2.0L derivative of the engine, which appeared in 1993. The early engine is identified by looking on the cam cover - on the front left hand side it will read 'DOHC 16V'
More to follow soon when I dig out the original Ford brochure.
Series 2 Zetec-E - 1995revisions were made to the cylinder head to combat sticking valve trouble caused by low grade fuel. Other small changes like improved spark plug leads and revised injectors, gaskets etc. This engine can be identified by again looking at the cam cover - it will read '16V ZETEC ' on the left hand side.
Series 3 Zetec-E - 1998 
Bar the cylinder head, this is a completely different engine. First introduced to the UK in 1998 it was installed into the award winning Focus & Mondeo
(left) The block has been significantly strengthened. The new engine has more metal between the bores
(the photo of the mk2 block shows how little metal there was on a 2 litre) and the oil filter is now incorporated in the base of the block. The sump is of a much better two-piece design - it features much improved webbing to reduce block flex, and also has a windage tray complete with baffle to reduce oil surge
(below).
right from the 2 litre engines launch in 1993 it was described as harsh by the motoring press, the new engine has Teflon coated pistons for smoothness/less friction, the bearing caps are also on a single piece frame for strength. The sump is a 2 piece item which features improved baffling. The cam belt also has a much improved tensioning system, as on the Mk2 only 3/4 of the exhaust cam pulley was driven by the belt. The hydraulic tappets are gone and replaced by solid variants with shims for adjustment. Solid tappets offer improved valve control at high RPM and surprisingly on this engine these are very quiet in operation!
The water pump is completely revised, it is an outboard pump with high capacity. This was the controversial part that caused the Focus WRC so much trouble at its rallying debut .
The injectors on the series 3 are different to thos on earlier engines. They are now the Bosch 'pencil' type injectors with a different (improved) spray pattern (larger cone). There are now two jets into each valve throat instead of the previous engines one. The ports have been slightly modified to suit
(right)The series3 Zetec was first utilised in America (Escort ZX2), the basic engine is identical except it has variable cam timing on the exhaust cam - this isn't there for performance like Hondas VTEC engine, but to comply with emissions regulations. It is called the Zetec VCT
The photo shows the American Zetec-VCT solenoid can be seen clearly under the cam belt cover. Two-piece sump visible also. On this particular example the block has been painted red and the engine also features a performance exhaust manifold - it is going to be installed into a 1980 RWD Ford Mustang
