Let’s talk about Ignition

I did a piece on Distributor Caps a couple years ago, and I wanted to continue with rotors and points.

There are a few choices of ignition parts available for a Vintage Ferrari, but if you’re only tuning up your car once every several years, or rely on you vendor to supply you with the right parts, you may not know the problems with the parts, or which ones you should try to avoid. Vendors will sell you what they have, and sometimes don’t know about the issues the mechanics have after they buy the parts. I can’t tell you how times I speak to fellow mechanics about our struggles and when we complain to the vendor, their response is “I haven’t heard anyone else complain!” Even if there is a problem, a vendor may assume (and sometime correctly) that it was the problem with the installer, but I wanted to make you all aware of some of the differences in the parts.

This is an original Magneti Marelli rotor. They are made of the translucent plastic with a contact point that is straight with no flare on the nose of the rotor. These rarely wear out and can often be put back into service with some light sanding and a cleaning, but after 30-40 years of service, they will eventually wear out, crack, or start arcing.

This rotor was in the car I was working on, and it too has a Marelli logo on the rotor, I believe it was originally made for a V-8 Ferrari as the nose of the rotor is wider, In fact the V-8 rotor is even wider and this one was cut down to work with a V-12 cap.

This is what is currently available in reproduction and I’m not impressed. The plastic is softer than the original rotor, and the spring clip keeps falling out. The clip moves inside the rotor affecting the height of the rotor, which can damage the center contact. When the rotor doesn’t fit due to the spring, the plastic will deform on the distributor shaft. I’ve also seen this version with casting flash from the plastic partially covering the center contact. I would pass on these rotors.

The black rotors are a little better. The plastic is a little harder, and even though the spring tensioner also falls out, it at least keeps the rotor properly tensioned and snug on the distributor shaft without it being too tight. The harder plastic also makes for a more positive seating on the shaft.

Both rotors will require trimming the T shaped nose off the end of the rotor to work with a V-12 distributor. The wider tip is made for a V-8 distributor that only has 4 contacts inside the distributor cap, with the V-12 cap, there are 6 contacts, and could allow the wider rotor to arc across the adjacent contact point.

Moving on to points. There are two versions of points that I believe are currently available. The one on the left is made of plastic and the one on the right is bakelite. The original points were bakelite, so I would imagine keeping the parts in original materials is better.

Be careful to inspect he points and the springs when they arrive. I’ve found many defects from manufacturing no matter who or what they were made out of. The spacing of each spring is specific because they are meant to bend into the shape of a U when fitted to the distributor.

If the springs are not riveted correctly, this U shape will cause the points to bind. I would also check the diameter of the pivot hole and make sure you use some lubrication when installing. I have a reamer that I can check for the proper diameter of the pivot.

Several years ago, I found this set of points that were improperly riveted causing the springs to bind when bent into shape. Check everything, and trust nothing!