so why not use the 75 engine?
The Punto 75 engine does look a better starting point than the 60 at first glance. It offers more bhp and torque, and it's the same size as the 60 engine, so why not use it?
Simple answer is that the cylinder head is designed to take the Punto 75 intake manifold with four fuel injectors as opposed to the Cento's one mounted in the throttle body. The bolt spacing on the head just doesn't match up, so your cento intake manifold and throttle body won't bolt up. You could fit the Punto 75 manifold, but to make it work with multi point injection you would need to have the Punto 75 ecu and engine bay wiring loom mated up to your cento - not too easy as the Punto ecu's sit on the opposite side of the engine bay or use a seperate ECU such as megasquirt but thats a lot more work & cost.
Getting the throttle cable matched up again might be tricky too.
The 75's ecu and injectors need to be supplied with between 2.5 and 3.5 bar of fuel pressure (depending on year of donor car) as opposed to the 1.0 bar that the Centos run at - something which you will need to address.
The 75 engine has a slightly hotter cam than standard, allegedly the same as Novitec offer for 1108's as a fast road option. if you're keen you could buy a 75 engine then do a mix n'match - 75 engine block +Cento head and 75 cam.
do not use the Punto 75 intake manifold with a SPI unit. we have it on good authority from Yannina and Smokeme who have tried it that this manifold is what's called a 'dry' one - it's not supposed to have fuel in it and it will suffer from fuel pooling and poor running. It will work, the car will run, but not at all well.
however If you feel like doing the 1242cc 16 valve(MPI) conversion,
it can be done but is quite an involved job. Clearance against headlights and bulkhead become an issue, as does trying to get an alternator to line up with the crank pulley. The same ecu and fuelling problems as with the 75 MPI engine swap will have to be overcome as well as other issues. You can't just bolt a SPI throttle body onto this one, I'm afraid.
In short, it can be done but will cost.
