Brief rundown on the sohc Fiat engine
available in the following sizes,
1116cc, 1290cc, 1299cc, 1301cc, 1372cc, 1495cc, 1581cc.
These are acheived with a combination of bores and strokes.
Bores sizes (std) 80.0mm, 80.5mm, 86.0mm, 86.4mm.
Stroke lengths, 55.5mm, 63.9mm, 67.4mm.
What Ahmed wants to do (I think) is take a 128 series engine (80.0 x 55.5 1116 cc combination) and install a 67.4mm crankshaft and rebore to 80.5mm (1372cc capacity) ... which will work, but unfotunately not with a combination of standard Fiat parts.
The 67.4mm crank from a Tipo/brava/bravo/uno etc etc will fit into the 1116,1290,1299,1301,1495 crankcase, with a slight bit of file work to the sides near the gasket face to allow a little clearance.
But the standard 1372cc combination from Fiat doesn't use the shorter of the two block heights used in the sohc engine series...
so if you install the long stroke 67.4mm crank into the short block you need to use either
A) very short conrods, and I know of none from the Fiat parts bin that will do the job. , so they would be custom items.
B) have different pistons made with a shorter compression height (distance from the gudgeon pin centre line to the top of the piston) again I know of no "off the shelf' Fiat items with the correct bore size and Comp. height, so they would be custom items
Another thing you need to know is the two block heights have differnt conrod lengths also, the shorter stroke 1116 and 1290, 1299 and 1301 cc combinations use a shorter cast con rod, whereas the taller block engines use a longer conrod which (most of the time) is a forged item.
SteveC