1986 Alfa 75 2.0 Solex Carbs Tune-up

[Basty]

Hey !

Is anyone willing to share their experience with synchronizing two twin-body Solex 40 addhe carbs on a 1986 2.0 Alfa 75 ?

I am thinking of doing this operation myself, i've purchased a Synchromate ( TecMate SynchroMate Throttle Valve Synchroniser ) and i really don't know where to start.

I believe the mixture is too rich ( very white exhaust smoke ) and when idling the engine is trembling so much that is almost coming off the chassis. Not to mention the nightmare of starting the engine. There are also often losses of power and engine choking.

Thank you in advance,

Basty

[Giorgio68]

First of all how old is your carbs. If they are not that old you will need to adjust the air mixture using the colortune if it is running rich or poor.
Colortune is a sparkplug with a glass clear top where you can see the combustion chamber and the color of the smoke. This way you can adjust the air mixture screw by looking into the sparkplug.
I bought mine from carbtune.com in England, IAP also has them in the US. I believe the sparkplug size would be 14mm on your Alfa.
I only test one cylinder just to see how it works, I have not done the car entirely.
I hope this helps.

Giorgio

[Ennio]

First of all, check the timing of the engine, adjust it dinamically with a timing light or do a static timing. Then you must buy carb cleaner, start the engine and spray the carb`s mounts, if the rpms change you should change the mounts as they are leaking air and you will be unable to do the carbs.

Then I recommend you take the carbs appart and clean them, if you haven`t had them rebuilt and/or cleaned for a long period of time.

There are two key things on carbs:
1)balancing them, so that all the cylinders get the same amount of air, and have a smooth operation and max performance
2) correct mixture on each cylinder

I would encourage you to read the posts on this matter on the carburettor and injection section.

First you must balance the air that the carbs are drawing in, and adjust them using the balancing screw, if more adjustment is needed you can use the screw on each barrel.

Once they are balanced you have to adjust the mixture on each cylinder and adjust the idle speed if it increases. The colortune Giorgio mentionsis a great tool, I bought it and used it along with a synchrometer and my alfetta gtv know is as smooth as ever!!

Here in this thread I posted the literature I used
Synchrometer type

[Basty]

Wow, thank you for your very useful indications !

The colortune sparkplug is indeed a very good investment if you have carbs. I was thinking of evaluating the mixture based on the sparkplug head's color. You know, black if it's too rich, white if it's too poor, brown-ish if it's ok but that would have taken a lot more time and wouldn't have been so precise.

The carbs have been cleaned a couple of moths ago, i've changed all the gaskets and replaced all the vacuum pipes and what not. Do i need to do that again ? I hope not.

Unfortunately it seems that the documentation on Solex carbs ( a real proper one ) it's impossible to find.

Once again, thank you for your replies !

[Ennio]

I think you won`t need to clean them up again. Andrews` article on Dellortos (has one for webers) is very useful on the tuning of the carbs, with his method you won`t need to take the spark plugs to adjust, but to check.

Your solex carbs are just like the Dellortos and webers, you need to adjust the balance with the balancing screw and the mixture with the idle mixture screws for each barrel..if you can find a 70s alfetta manual, they have the diagrams of webers, dellortos and solexs.....