I agree with bmarler. The original distributor if in order is perfectly capable of doing a good job. Indeed, you will be surprised how accurate the timing curve is. If new original distributors were available I would replace any worn distributor by an original distributor. Good quality and well adjusted contact points last very long if the condenser is replaced every two years. With modern electronic dwell angle meters checking the gap is quick and easy. If the dwell angle is around 57 degrees, it is ok.
I use plugs with built in resistor to reduce peak current and suppress radio interference at the same time. Also I use plug cables with a wire wound core of stainless steel resistance wire. The resistance and inductance reduce peak currents even more and trade high peak current for longer duration of the spark.
When using normal plugs like NGK BPR7ES the Fulvia is very sensitive to the gap. Set the gap to 0.6mm. When the plugs are new the gap is more than 0.6 mm. Iridium plugs like BPR7EIX I leave at the factory set gap. These plugs last very long.
If the fuel air ratio is correct, the mixture burns easily. Check if any attempt to “improve” ignition is not an attempt to mask bad mixture. After 50 years corrosion and wear of the carburetors is more likely than wear on the distributor.
Having said that, the 123 dizzy is an excellent distributor. Remember to select the right curve. DO NOT install the vacuum version. Even if you do not connect it to the vacuum it will react to going up and down the mountain. I install the TUNE only if there is VERY GOOD reason. The factory provided curves are good and cover many types of fuel under many atmospheric conditions and altitudes. Put the original dizzy in the boot.
I set the fixed advance to factory spec to within a degree. Due to the narrow V construction of the engine the crankshaft is short and has only three main bearings. There is no room for a wide bearing in the center. The center bearing is very narrow wile it serves two con rods in near position and 2 in second position.
If the mixture is ignited earlier it means that combustion is finished earlier. It is a long time ago I rode bicycles. I do remember though it is important to apply power to the pedals at the right moment to arrive at the destination without overtiring myself and without destroying the crank. If the combustion is finished early the load on the crankshaft bearings (main and con rod) increases rapidly. Also the load increases on the head, head bolts, piston rings, cylinder walls etc. The center bearing of the crankshaft will be on the copper very quickly.
I learn a lot from the Fulvia (and Flavia).
Watch the following movie.
https://www.youtube.com/watch?v=fPXkUXXFoCw
The difference between the tigers and the gibbon is that the tigers have their weight under the pelvis. The gibbon has its weight over the pelvis. The latter is unstable but infinitely more flexible. It requires quite a bit of computing power to coordinate its movements. It is not only the brain power, every cell, every tissue, every bone has its function in the distributed computing process. The bones look very much like mechanical function generators as for instance found in the Kugelfischer injection control unit.
The Fulvia (and Flavia) have the weight (at the front) on the upper wishbone thus on top of the swivel. It is an unstable situation like with the gibbon. A mechanical computer keeps it stable. The aluminium towers, double wishbones, swivels, cross members control the position of the wheels with computer precision. The paleontologist says the bones determine the animal. If I study the bones of the Fulvia I associate it more with agility and precision than with power, much like the gibbon. That also means millimetre precision in all bones. You will be surprised when you measure the body and sub-frame. Most are distorted. Quite a few special and standard tools are needed to make sure the body and sub-frame have the correct dimensions. Interestingly my piano tuner, who also restores concert piano’s, recognized the function of the bones of the Fulvia berlina immediately. The coupé? Mmmm. Not nearly as beautiful as the berlina. Nevertheless, agility is what the Fulvia is about. Like the gibbon. See how the gibbon manages to keep his speed when turning corners. Has nothing to do with power. Power becomes an issue for the gibbon if he breaks a bone and it heals under an angle. He looses the millimetre precision. He must turn corners slowly. On open ground the tigers my be faster than the gibbon. When driving your Fulvia stay away from motorway and race tracks unless you are a masochist.
The question is do I set the factory timing while many forum posting suggests to advance the timing a bit. The answer is yes. Motivation above.
Since we are supposedly going though a Corona crisis, there is more to learn from our Fulvia. Often the word “better” is used in combination with changes such as advancing ignition more. The criterion for “better” is not specified. Better has no objective meaning. It cannot be anything else than the the projection on the car of an old personal trauma, which is most likely anchored on L3 (lumbar vertebra nr 3). In my case L5. Agility is the victim. Movement is limited to straight forward and the directions become better or more. Sometimes the cosmos requires to move in different directions such as backward or up and down. This turns out to be impossible. More power is applied to move in the wrong direction even longer. The crisis is invented.
Don’t believe anything I say. Looking at the picture I paint is ok. Not too long though.