Hi Abe,
better use 45 or 48 Twin choke Webers or Dell 'Orto's and a Politecnic / Sodéma camshaft. Only 40 Twin choke carburettors are too small and won't bring that much performance.
For the airbox , you can copy the Murena S airbox . You can also modify a Alfa airbox , but is is rather boig and you don't have much room there.
I'm sorry but I disagree with a lot that has been said in this thread.
The first thing is that the Murena 2.2 needs a much better camshaft before you start fitting bigger and twin side-draught carbs. For instance the Prep 142 or 'S' will actually run just as well with the original single progressive down-draught Solex and give much better consumption too. The Prep 142 and 'S' camshafts are not that great really and the original power figures were over stated. As explained on my website, the standard 2.2 actually produced 113 bhp, the Prep 142 gave 136 bhp, and the 'S' gave 134 bhp. I have proved that the Holbay Tornado fast road cam profile with a standard down-draught Solex 34 CICF can produce around 140 bhp and give 28 to 34 mpg which is better than either the 142 or 'S'. If you want proof, check with Anders Dinsen who had my Prep 142 with the standard down-draught carb.
So if you want greater power than the Holbay or equivalent fast road cam profiles you will need an even better cam profile first, AND then you might need the twin 40 or 45 DCOE or DHLA twin side-draught carbs. but then you will have a further problem... and that is the manifold to put them on. The original Prep 142 and 'S' had a specially designed inlet manifold which moved the LH carburettor over to the right and lifted them both such that the intake was above the fuel tank and the end throat was not seriously restricted compared to the others, and a decent air box could be fitted which picked up cool air low down. This is necessary since allowing the engine to breathe the very hot air from the top of the engine compartment is bad. The special manifold also included a coolant extension on the RH end which none of the non-genuine inlet manifolds provide, so you will have to make up something yourself.
All the non-original intake manifolds including the Politecnic one are not good enough and are a compromise which will seriously restrict the intake and therefore the power produced. Furthermore some of these non-genuine manifolds cause fitting problems with other items such as the coolant pipe under the manifold, and dipstick tube; and all the modified engines with twin side-draught carbs. will drink a lot more fuel and will often drop into the teens when running around in urban environments. Only on long runs with a large portion of cruising will the car produce 28 mpg or above.
The Politecnic cam was not available last time I checked - he might have your existing camshaft re-profiled but then you can get that done here and cheaper.
As for the 2.2 engines modified by SCU - I have never yet found a decent one! They are all not much better than standard if indeed they are better - many are actually worse, and they use far more fuel too.
If you don't understand how a poor intake can seriously affect engine power then ask Titus who has seen 6-8 bhp differences for relatively simple difference in the intake system. And you can't make and fit an airbox similar to the Prep 142 or 'S' on the twin side-draught carbs. fitted on a non-original manifold as there will be no room. You might just a get very thin 'pancake' filter on the left hand carb. which is almost up against the fuel tank; but these are restrictive and again you will be picking up the very hot air from the top of the engine compartment. Not only does this restrict the power (hot air contains less oxygen) but the hot air means higher combustion temperatures and they are already hot enough without adding to it. This can be one reason for many of the failed heads or gaskets.
Roy
I experienced exactly what Roy speaks of, first hand.
When I bought my, it was Running an "s" cam, with a pair of 40mm sidedrafts on a politec inlet manifold.
If you are not going for more than 140-150 hp, I'd say you are much better off with keeping the stock inlet manifold/carb/airfilterbox.
I had a ride in Anders car way back when he bought it, and it was just as fast, if not faster than mine, and it ran smoother as well. (though the sound of the side drafts is something else).
