International Lancia Forums

Hi to all from Russia! )
Technical advise needed! In my 2-ser. Fulvia 1,3s I've got solex 35 carburetors. I would like to improve, as possible, driving and, especially, acceleration parameters of car. Heard, that Dellorto carbs are some way better in reaching this aim. Found some offers, but they are rather expensive! )) So, will the carb change be better, than any improvement of existing solex? ..Will dellorto really be better, than solex in "alive horsepowers" and dynamic? Or the profit will be miserable? I mean, in plain words, does the game worth candles? ))
Thank You!

Hi,

Solex carbs are often blamed for being inferior.
But, if they really are, Lancia would not have used them!

My experience is that when they are properly set up and without excessive wear on the spindle (weak point here), they are perfectly ok and will provide many years of trouble free performance.

Downside is that they are difficult to tune. For sure, the jet size and especially the mixing tubes as developed during the sixties are not optimal for today's petrol. (maybe in Russia it's not so bad...)

For changing the main jets , you will have to remove the whole carbs. Terrible job, which is much easier if you replace the M8 nuts by M7 nuts (11mm socket) which you can tap to M8. Now, a normal socket spanner will fit and you have the carbs off in 10 minutes.

Mixing tubes are the trick. You will find that there are many different 'original' tubes, with much different characteristics. Mixing tubes can be easily adjusted; drill new holes higher or lower in the tube and plug the other holes with a drip of epoxy glue.

If you don't have a rolling road and much time/money, the best way to tune your car is to buy/borrow a wide band lambda sensor, like Tech-Edge (http://www.techedge.com.au/) and just experiment. You will find that mixture will not be constant during different conditions of load. For normal driving, low load, you want a leaner mixture. 1liter to 14km is possible, 450km on a tank should be normal. This is done mostly by the mixing tube in combination with main and idle jet. During acceleration and high load, you want the mixture to be close to 0.8. To have that during the whole of the rev range, that is the difficult part.

Make sure you have the camshafts timed to spec and your ignition is well set befroe you start messing with fuel. If you got the mixture right, then you may advance ignition 2 or 3 degrees for further improvement.


Tuning like this is very rewarding. You will find that your car can go much faster with really good setup.

Your performance may be further increased if you do some work on the inlet ports in your cilinder head. And exhaust manifold and silencer.

I would start with above points first, before investing in exotic carbs.

Bart

WOW!
Thank You for such a complex answer! ))
..will need some time to realize all written above!

Dell'orto 40 DHLA would give you more tuning flexibility on choke (main venturi) diameter and jetting than the original Solex.

But both Dell'orto DHLA and Weber DCOE have a wider barrel spacing than Solex. So you will not be able to mount the DHLA on the same intake manifold; you will need a "Group 4" manifold, or a manifold adapter to mount the DHLA.

Dell'orto solved this problem for the Fulvia by manufacturing a special carb type--DHLB--with the same barrel spacing as the Solex, so that they could be mounted directly to the original intake manifold. The DHLB were only made in 35mm, but they do offer better performance than the Solex. Unfortunately 35 DHLBs are very expensive now; if you can find them, a pair may cost 750 euros.

So I wouldn't rule out rebuilding and properly tuning the Solex.

Thank You!