The 1.6 had a Weber 36 DCNVA 16, whilst the 2.2 had a Solex 34 CICF 141 (TAL 13116.000). These are both twin-venturi downdraught type units, although the Weber is a simultaneous opening one whilst the Solex is progressive. If you're not sure what that means, the Weber is like two carbs. in one and both throttles always open and close together; whereas the Solex is like a single carb. at small throttle positions with only the primary throttle opening and a twin carb. above approximately two thirds throttle, when the secondary throttle starts working. That makes the Solex more economical in general road use. The Murena Prep 142 & 'S' models had two Solex twin-venturi sidedraught units similar to the well known Weber 40 DCOE type carbs. Some Prep 142 may have had the Solex C40 ADDAE, whilst others and the 'S' had the later C40 ADDHE versions. As with all carburettors, the specification numbers define the exact settings and you should always match these carefully if you replace them. Even small changes can give widely different Venturi, Auxilliary, and Jet settings, which may make the difference between the car running properly or not... and just an incorrect float level can prevent the engine running properly!
To give you just one example, the 34 CIC listed above (13116.000) has the following specs.: Auxilliaries: 4.0 Venturis: 25 primary 26 secondary. Air correction jets: 190 primary 180 secondary Main jets: 127.5 primary 135 secondary... whilst a 34 CICF 161 (CIT 12572.000) sold supposedly as a replacement has the following specs.: Auxilliaries: 3.0 Venturis: 24 primary 27 secondary. Air correction jets: 180 primary 200 secondary Main jets: 130 primary 122.5 secondary. There are other differences too, like emulsion tubes, but I think you can see from these figures that they are not the same, by a long way!
First, for carburettor spares, one place I have found very good is Eurocarb Ltd, Reading. They are mainly Weber and Dell'Orto specialists but worth a try for Solex.
If you have a 1.6 Murena with a Weber carb. there are usually plenty of spares still available to overhaul and repair it when necessary, and there may be the odd place who can still sell you a new carburettor if you wish. Seal and gasket kits are certainly available.
If you have a 2.2 Murena then the problem is that Solex spares are now difficult to get hold of, although it can be possible. Try Webcon, Sunbury who although Weber agents had large stocks of Solex spares too. There may even one or two places who say they can supply new Solex carbs. (old stock probably) but please bear in mind what I said above about the correct specifications. Again, seal and gasket kits are still available. If you change the needle valve, please make sure they are exactly the same as any change will alter the float level and cause problems.
If you can get an original replacement, then this is usually the best option, since the manufacturer spent a lot of time and money getting it right in all respects. However, this may not be possible, or you may want to try and improve the carburation, at the same time as replacing it. However, you should remember that the orientation of a carburettor is very important. You cannot fit a carburettor from a longitudinal engine to a transverse engine, or if you insist, you must rotate it 90 degrees, so it faces the same way relative to the direction of travel, as it did originally. Also when changing to a different carburettor, it is always best to have the car set up professionally, preferably on a rolling road. You will then know that it will drive correctly in all conditions, not be too weak or rich at any point, both which can damage an engine, as well as giving inferior performance and fuel consumption, and probably causing excess pollution.
The Solex 34 CIC can be replaced by a Weber 34 DMTR which is the carburettor fitted on many Citroen CX's. However, there are many different specification 34 DMTR's available and the problem has been trying to find out which one is a direct replacement or at least, is as close as possible to the specification we need. Some will physically fit in every way, provided you have the later throttle linkage - the early linkage will foul the choke diaphragm; and one even has almost the ideal venturi and jet settings etc., but it has no vacuum take off for the distributor advance mechanism. Until I can give a definitive answer, I won't recommend any. I have seen a number of different versions of this carburettor fitted to Murena, but none so far have been correct in all respects which means they needed some modifications. It may be that there is no ideal replacement, and whichever is chosen it will need modifying. If this is the case, then we need to find the one that needs the least changes.
If you have found a 34 DMTR that is just right in every way, please let me know the specification and part numbers, so I can pass on the information. Once I have found the best option, and what changes, if any are required, I will put the details here. Watch this space, as they say!
The twin sidedraught carburettors fitted on Prep 142's and 'S' models required a special manifold and air box as the space is quite tight. You can obtain an alternative manifold and modify it to fit as some owners have done, but usually these other manifolds are 'flat' whilst the original was tilted up at 15 degrees so that the carburettors and air box were lifted above the fuel tank. A horizontal manifold will mean you cannot fit an air box, and the intake on the first venturi is almost right up against the side of the tank. You might consider not fitting an air box anyway, or you want to fit 'pancake' type filters, but please realise that the air at the top of the engine bay is extremely hot and you do not want the engine breathing this! The original air box was connected to the original air filter above the transaxle, which picked up cooler air from low down behind the block. Cool air is denser and provides more power as well as helping to control the engine heat.
The second point to remember, is that these carburettors are unlikely to give you more power than a good twin-venturi downdraught set up, but you will use more fuel! You certainly do not want big sidedraught carbs. say 45 or 48 DCOE's. The original Solex were only 40's for good reason. Power comes from having good breathing, and a better camshaft is needed before going up in carburettor size. The Holbay Tornado 58C fast road cam profile is better than the 'S' cam but will still happily produce the power with a twin venturi downdraught carb. There is also a restriction in the exhaust port that will ultimately restrict the breathing of a standard head, and it cannot be opened up since you will go through to the water jacket.
If after all this you still wish to fit some twin sidedraught carburettors, then the obvious ones to try are either Weber 40 DCOE's or the Dell'Orto equivalent. Since the supplier is unlikely to know the Murena S spec. you should give them the Solex specifications and that may help them to provide an equivalent set up.
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