There are 3 engine types Ford have used in the last few years

Sigma

Zetec

Duratec

Unfotunatly ford use the names like monkeys swing on tyres!

Duratec's are all alloy and are great.

Simga are what most people call zetec;s and are cast blocks with alloy heads, they are cheap and cheerful!

Zetecs are good engines but are expensive.

Alex