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The Metro was introduced in October 1980 as a replacement for the Mini. Fortunately for the Mini, the Metro didn't do as well as expected and the Mini continued in production. The Metro used the A series engine (but the newer A+ version) and was available in 998cc (45 BHP) and 1275 (62 BHP) versions. Fortunately again for Minis, these Metros offer a great source of parts. The Metro even offers better brakes that may be used to dramatic effect on a Mini. Racier versions of the Metro were introduced including the MG Metro (1275 with 73 BHP) and the most powerful production A series ever, the MG Metro Turbo (1275, Garrett T2 turbo, 95 BHP).
1990 saw the new Metro introduced with a new body-shell, better corrosion protection and the excellent K-series engine mated to a Peugeot gearbox. The K series was originally available in 1.1, 1.4 and 1.4 fuel injected 16v versions though later, even the 1.1 versions were fuel injected. The K series model didn't seem to make it as an export model as many visitors to this site wonder what we in the UK Are talking about when we discuss it. For those people, here's a couple of pictures:
This engine is a cheap alternative to either a kit or ready-built unit from the likes of Mini-Sport. While it doesn't offer the huge power you might wish for, it still offers a respectable 73 BHP with excellent reliability. Parts are of course standard and very easy to get hold of. Typical price for a complete unit including ignition, carburettor, inlet, gearbox and ancillaries is around £150.
The MG Metro engine achieves its power increase over standard 1275 engines by having a much improved cylinder head and a suitable camshaft. Fuel economy doesn't suffer too much and other than changing the bolt-on engine mounts to suit the Mini, it's a simple drop-in replacement. If you're buying an MG Metro engine, it's a good idea to see if you can buy the brakes and running gear, as the calipers are 4-pot with vented discs. Try and use the original air filter as well. The black plastic pan appearance might not be too attractive, but according to David Vizard, it flows reasonably well. As for the rumour that the MG Metro filter box doesn't fit in the Mini engine bay, I've never had a problem with mine (OK so it's a bit of a squeeze).
MG Metro Turbo
This engine is the most powerful A-series derivative in a production car. It uses a Garrett T3 turbocharger at around 4 to 4.5 PSI which achieves 95 BHP. The engine can be readily picked up from scrap yards for less than £200 but try to ensure you get as many parts with it as possible especially the turbo itself and the carburettor. Note that it's probably a good idea to get the original fuel pipe hosing or ensure that you use a sufficient bore as fuel starvation may occur otherwise.
The Metro Turbo engine is not a simple drop-in replacement although it's still much easier to fit than some of the hybrid engines on this website. Certainly, you will have to modify the bulkhead to allow room for the turbo-charger and exhaust manifold. This is usually done by welding in a box made of material of similar or greater thickness than the bulkhead material to avoid weakening the structure of the bulkhead.
You'll have to be creative to protect the wiring loom from the increased heat output in the engine bay. Cooling vents in the bonnet may help and thermal blanketing and exhaust wrap are recommended. To cool the engine itself, it's unlikely a standard Mini radiator will do the job adequately. In this case you may have to fit an auxiliary radiator or replace you radiator with one of the high efficiency units sold by Mini-Spares and others. Alternatively, you could attempt to fit a front-mounted radiator from one of the later Minis. Some oil cooling may also be necessary but ensure you use a thermostat as oil that's too cool reduces its effectiveness.
Matthew Green's web site provides an excellent description on how to fit an MG Turbo engine: click here
Tuning the A Series Engine
Metro K Series
This engine is the most recent Metro engine and is available in several forms including a 1.4 fuel injected, 16 valve version. Although you might think it would be the most natural selection as an alternative engine for a Mini, it's not been very popular due to it's physical size. However, some people have persevered and had some excellent results. Here's some links to sites which detail how the K series engine can indeed fit into a Mini!