Roy's Matra Enthusiasts pages
FAQ's: Frequently Asked Questions
- What carburettors were fitted to the Murena models?
The 1.6 had a Weber 36 DCNVA 16/100, whilst the 2.2 had a Solex 34 CICF 141 (TAL 13116.000).
These are both twin-venturi down-draught type units, with progressive opening. The earlier Weber 36 DCNF on the Bagheera was a twin-venturi simultaneous opening type, but the later 36 DCNVA on the Murena 1.6 is a progressive. If you're not sure what that means, a simultaneous opening carb. is like two carbs. in one and both throttles always open and close together; whereas the progressive 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 progressive more economical in general road use. The Murena Prep 142 & 'S' models had two Solex twin-venturi side-draught 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, Auxiliary, 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 CICF listed above (TAL 13116.000) has the following specs.: Auxiliaries: 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 (but actually for a CX2400) has the following specs.: Auxiliaries: 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 you can see from these figures that they are not the same, by a long way! Note the TAL and CIT in the specs. TAL=Talbot and CIT=Citroen if you hadn't guessed!
One thing about the Solex 34CICF on the Murena 2.2 that might catch you out, it doesn't appear to have an idle mixture screw. It does but it is not visible as with older carbs. The reason is that tighter emission controls were just coming in at that time, and these carburettors were more accurate, set up correctly and then 'sealed' to prevent tampering. The mixture screw is buried in the base flange going horizontally left to right, is gripped with threadlock to prevent movement and may have a sealing plug fitted to prevent access to it. If you should need to alter it (although you might question 'why?' as it should never need it and the problem will probably lie elsewhere) you will have to dig out the sealing plug if it's still there, and then when you turn the screw you must make tiny adjustments with plenty of time to settle between each one, as these are much more sensitive than the older carbs. (with external mixture screws usually gripped with springs around them to stop them turning on their own). In fact you really should have it on a gas analyser as you won't really be able to detect when the emissions are correct otherwise. These are not carbs. and engines that can be tuned by 'ear' any longer as with older cars.
- My Murena Weber/Solex downdraught carburettor is worn out. What can I do?
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 Eurocarb or Webcon, Sunbury who although Weber agents had some stocks of Solex spares too (and jets are often common anyway). 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 CitroŽn CX's. However, there are many different specification 34 DMTR's available and since the venturis are cast-in unlike many Weber where the venturis are changeable, they cannot be removed or replaced so 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!
By the way, if there are any Murena still around with the Tagora 2.2 down-draught inlet manifold and either the 35 TMIMA or a Weber 38 DGMS or DGAS, these will never work! These carbs. are for longitudinal engines and won't work on a transverse one!
- Can I fit twin side-draught carbs. to my standard Murena 2.2?
The twin side-draught 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 'straight and flat' whilst the original lifted the carbs. and importantly moved the left carb. over to the right, so that the carburettors and air box fitted above the fuel tank. A plain 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 more dense providing more power as well as helping to control the combustion chamber temperature by keeping the air intake cooler.
The second point to remember, is that these carburettors are unlikely to give you more power than a good twin-venturi down-draught set up, but you will use more fuel! You certainly do not want big side-draught 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 down-draught 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 side-draught carburettors, then the obvious ones to try are either Weber 40 DCOE or the Dell'Orto DHLA. 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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This was last updated 5th April '21