The base spec 1.8 litre Zetec makes about 115bhp in standard trim. The 130bhp 1.8 is the same engine fitted with different camshafts, and this engine can be found in the Fiesta RS1800i. The cams are interchangeable, so a 115bhp unit will become a 130 with the addition of the better RS cams.
For most people, the 2.0 engine is the engine to go for. It makes around 135bhp as standard, but theres so much more available with some mild tuning.
Ford uprated the Zetec during 1997/8 model year, following its introduction back in 1992. The earlier engines known as Silver Tops (ST's), thanks to their plain aluminium cam covers, with later engines being known as Black Tops (BT's) because of their black cam covers. BT's have two piece sumps whereas ST's make do with a one piece design. Changes mostly relate to the front of the engine. ST's have a standard water pump which bolts on to the engine, but BT's have a cartridge type pump that sits in the cover itself. All engines since 1996 have a concentric hydraulic clutch release bearing. And finally, the Zetec weighs in at about 115Kg as opposed to the Pinto which weighs in at around 133Kg.
Although the engine fitted to the Focus ST170 has Duratec emblazoned on the cam cover, it isn't a Duratec H4 at all. Fords marketing department presumably decreed that their top-of-the-line performance variant couldn't have an engine of older design than the cooker models, and so they dressed up a Zetec to look like the engine that replaced it. The Duratec H4 is an all alloy engine with chain-driven cams and the induction and exhaust on opposite sides of the head to the Zetec. The ST170 engine is basically a trick Zetec with a stronger bottom end and variable inlet cam timing. Some specialists say that the engine cannot be transplanted because the variable cam timing is controlled by the ECU in the Focus. However, one way of altering the cam timing would be to use the shift change lights output from an ECU for instance.
Block, crank and rods
The reason the Zetec lasts so long and is so reliable is because it's built to standards that ordinary car engines just weren't built to 20 years ago. The tolerances, materials, machining and assembly are in a league that your average Pinto can only dream about. There have been engines with mileages of 170,000 reported with honing marks still on the bores. If you do manage to find a knackered bottom end, dont bother trying to recondition it. The engine was developed with Yamaha and the boring/honing process of the iron block is very hard to replicate. It can be done, but as you can buy a brand new short engine for £500 there's little point in reconditioning and old engine, unless you are going for an overbore of 2.1 litres. This can be done using Vauxhall XE pistons. The bottom end of the Zetec is good for 7000rpm in standard form and, with the addition of ARP bolts, 7400rpm is no problem. Thats about the limit for a road engine but if its a top spec race unit you want to build and you are looking for more than 200bhp, then you'll need forged pistons and steel rods in order to safely rev higher than this.
Starter motor and alternators
Zetecs are usually saddled with a 60 or 70amp alternator to cater for a modern cars' power-hungry electrical system, with their electric windows and air conditioning. The problem is that it will probably get in the way of the carbs or throttle bodies you want to use. However, you're unlikely to need an alternator with that much power so to gain some more room you can replace them with a Lucas or Brise alternator. I'm using the Brise version, which is a very tiny 49A model.
Starter motors are pretty straightforward as one from a Ford CVH engine (Lucas part number LRS707) will bolt straight on. You can also use one from a Pinto engine, although it will need a 14mm spacer between it and the engine to give the correct pinion throw.
Heads and cams
Like many four-valve modern heads, the alloy Zetec unit is pretty good straight out of the box. It has good tumble which allows it to produce a healthy torque curve but that is not to say that gains can't be made. Careful porting can provide worthwhile flow improvements and there's room for bigger valves if you're after more than 200bhp. A standard head (on a 2.0) with side draughts or throttle bodies plus mapped ignition will make between 160-170bhp. Port the head and add some 285° cams for 200bhp. With big valves and careful gas flowing you can squeeze 220bhp. You'll need vernier cam pulleys to get the best out of even standard cams.
There are plenty of cars out there with RWD Zetec installations using a standard 1.8 litre sump and its associated pick up pipe. For road use his works fine. However if you are planning the odd track-day or want to go racing you need a sump modified to suit RWD. These are available (together with dipstick and dispstick tube) from several vendors. Dont go too big on oil capacity. The Zetec needs to run oil temperatures of above 100°C which is why it only has a 3.8litre sump capacity. If the oil temperature falls below this engine wear increases rapidly.
ZVH Turbo conversion
There's a popular engine conversion available in the UK, called the Zee-VH. This involves combining the Ford Zetec engine block and crankshaft, and the Ford CVH cylinder head and water pump. Sounds strange? Well, its popular amongst the Ford Escort and Fiesta Turbo owners. It allows them to build a higher capacity engine than the original CVH engine (1600 cc) and it also allows them to retain the original manifolds and Turbo system. Figures of up to 270 BHP have been quoted with this straight forward modification. Jim Hearne is currently producing some information on the Zee-VH and rather than re-invent the wheel, follow this link to Jim's site for all the technical details Zee-VH information page.
Another engine conversion that follows the Turbo route, is of course the Zetec Turbo, where the 16V head is retained. Sunny Khalsa's Zetec Turbo powered Mk3 Fiesta recorded 178MPH at Bruntingthorpe in September 2003, and he was planning to break the 180MPH barrier for a front wheel drive car in 2004.
Another excellent web site full of photos and technical information on the Zetec, is Mark Stewarts site. www.mstewart.co.uk. Mark spends a lot of time and effort documenting the differences between the revisions of the Zetec and the newer Duratec engines. An excellent site.