Distributor Cap Details

Distributor caps on a Ferrari were made by Magneti Marelli and were installed on several Italian cars in the 60s. Reproductions have been available for many years in varying levels of quality and accuracy. The one on the left is a reproduction my customer obtained and I wanted to compare some of the differences with an original cap that is pictured on the right.

There are a bunch of little details on these caps. On 6 cylinder caps that run half the cylinders on a V-12 Ferrari. #1 cylinder is approximately in the 7 o’clock position and the rotor turns in the clockwise direction. The three screws that hold the distributor in place are white cadmium plated slotted bolts with an 8 millimeter hex head. Below the head is a lock washer (or split washer). There is a Magneti Marelli logo embossed in the center of the cap. The original color of the cap was a dark brown, and tends to get darker as they age.

The color on this reproduction cap (left) is pretty good. Older reproductions were black. The screws on this reproduction are incorrect gold cadmium plated phillips head hex bolts. The numbers on this reproduction are incorrect for Ferraris as #1 cylinder is labelled in the 5 o’clock position and is numbered in the counter clockwise order. Also, the numbers seem to be sealed in place with a daub of yellow tinted epoxy while the original numbering was just plastic covered labels. I believe as the original labels aged, they yellowed, but started out white. Using this cap is not a problem, but the labeling has a lot of little issues.

Internally there are also some differences in the caps. The original caps had two length screws to stake ignition wire to the cap. Two long screws secure position #3 and #4 because the posts for these two positions sit further inside the cap.

The reproduction cap uses the same length screw for all the positions, which is not a huge problem until the screw head wears and gets stuck inside the post.

The longer screws with the original cap makes it easier to reach the plug wire with the deeper hole.

Now you know more about Ferrari distributor caps than most!