This https://www.fiatforum.com/punto/425910-coming-soon-elx95-mk1-cab.html might interest the Sei forum

should be a no brainer as I have read a few times that the 1.4 and 1.2 16v heads are identical, its just the Inlet manifolds and headers that differ.

That's good news - if the heads are identical that must also mean that the 1368 pistons, even though bigger bore, have similar pop-up shape to 1242 pistons, above 'deck' (where they rise into the head's combustion chamber), should clear the valve heads, and should give same CR as a 1368 motor, even tho using a 1242 head. Does that sound right?

What about our hope that the unaltered 1242 sensors and ECU will compensate for any effects of the bigger capacity? Should we increase fuel pressure a bit?

Been done several times.

It all physically fits, you'll need to use your 1242 head because the 1368 head has a different exhaust manifold stud pattern. Sensors all fit. However the ecu, whilst it will run it, won't run it perfectly well.

from fitting the mk1 1.2 16v to my cinq, i can say the mk1 1.2 16v ecu pretty much struggles to even adapt to the engine it's meant to be designed for! it's not the best unit by any means, it's hugely compromised. I can certainly see why people have issues getting it to run nicely on the 1.4 and generally end up going for megasquirt.

mrcinquecento said:

It all physically fits, you'll need to use your 1242 head because the 1368 head has a different exhaust manifold stud pattern. Sensors all fit. However the ecu, whilst it will run it, won't run it perfectly well.

Click to expand...

Warning the top head of the 1.4 16v have oil hole from the block to the head to lubricate the camshaft adjusting system (when you have)
And when you have that, the exhaust manifold of the mk2 is ok but the inlet not due to a bigger entrance and into the manifold you have a flap to pass from 8 to 16v !