jjhepburn said:
I am about to try the exact same thing today

I have an 1108cc engine from a 1992 Uno 60S and I am putting it into my 1987 Uno Sting (had a 903cc, then it got a 999cc and now its getting a 1108cc)
I believe the stroke is the same on the 999cc and 1108cc since I replaced the timing belt on this engine and it was the same part.
The stroke is different according to the Haynes Manual. Both the 999cc and 1108cc have the same bore of 70 mm, but the 999cc has a stroke of 64.9mm compared with 72mm for the 1108cc.
However, the physical block might well be the same size as an increase in stroke can be had simply by using a different crankshaft. I'm not 100% sure with regards to this though.
It is a fact that the 1242cc engine IS taller (the stroke is longer still), and that's why a spacer is needed.
jjhepburn said:
The upgrade is worthwhile, in my opinion, since the 999cc is 45bhp and the 1108 is 60bhp, thats a 30% increase in power without much (if any) increase in weight
The 1242 SPI engine is rated at 60'ish horsepower. The 1108 in the Cinq Sporting was rated at 55hp, and I even saw one magazine quote the Uno 60 1108 as 50 hp
Going by the Haynes manual again, the power and torque figures are as follows:
Engine -
Power -
Torque
999cc - 33 KW at 5250 rpm - 78 Nm (80 NM up to mid 1988) at 2750 rpm
1108cc - 37 KW at 5250 rpm - 87 Nm at 2900 rpm
Very little difference in power, but quite a nice increase in torque!
jjhepburn said:
Also since it has a larger bore the 1108cc uses a slightly larger carb (32 TLF 252 as opposed to the 32 TLF 250 used on the 999cc).
The carburetor is physically the same size! The 999cc is the Weber TLF 4/252 (and 4/251), and the 1108cc is the Weber TLF 27/251. Both have the same sized venturi (22mm) which is the physical size of the barrel inside, so the differences only come about with the jetting.
In fact, looking at the specs, the only differences are in the size of the full power jet (0.50mm compared with 0.55mm), idle jet (0.47mm compared with 0.45mm), and the superfeed jet (0.40 mm compared with 0.45 mm). These are very small differences.
However, the specs for the TLF 4/250 (fitted to earlier 999cc FIRES I suspect) are less clear. But again, the venturi is still 22mm.
Saying all this, it's probably still a worthwhile swap because at the end of the day you will get some extra power and more importantly, torque.
Though going by what I've read, the real secret to unlocking power in the FIRE engines is in the head. All the SPI engines (999, 1108, 1242) have the same head. The ports are on the small side, as are the valves.
The Punto 70/ 75 MPI 1242 has bigger ports and valves, along with a higher lift camshaft. On it's own the camshaft is supposed to take the 999cc from 45hp to 60hp! Swapping the head over is better still, and the bigger valves and ports allow more scope for tuning as the engine is breathing better. I've been told that the Weber 32 carburetor will still run quite happily at these power levels!
But I haven't tried these myself so can't say for sure if it will work.
I'm hoping that if I can save up some cash by next summer I can go and buy a Punto 75 engine and run it on a carburetor in my Uno. At the moment it is too cold and I've got nowhere to do the swap. And I'm strapped for cash! But it would be good fun to see what that engine would be like pushing my 20 year old Uno around :devil: