Has anyone experienced wear on top of the distributor rotor due to the contact button in the distributor cap in the photo below? This was after 5k miles as I was doing a service, it's almost worn through the metal. Everything was rebuilt before and the rotor came from Superformance, the cap from a west coast supplier. I took a quick look at my old cap/rotor, the immediate difference I noticed was the button had a lighter spring and didn't protrude as much. The button feels like a coarser material on the new cap. I had assumed these were a self lubricating carbon contact but clearly something is incompatible or I need to add a lubricant. Thanks, Andrew Image Unavailable, Please Login
No need for lubricant. Are you sure the rotor was fully pressed down on the shaft? Is the new rotor installed height the same as an original? How does the carbon button and the area around it look? Any abnormal wear apparent? Something's amiss.
Yes, I confirmed the rotor was fully pushed down, checked the dizzy shaft too. I need to start measuring a few things to get to the bottom of this.. agreed something is amiss
I suspect it is rubbing the coil tower in the cap and not just the carbon. Is it a reproduction cap? If you have a set of calipers or a machinist rule do some measuring.
Andrew, Have a read of https://www.ferrarichat.com/forum/threads/rotor-arm-and-distributor-cap.221531/ I noted quite a bit of variation in rotor dimensions, even from same supplier. It’s worth checking the rotor height and alignment with distributor cap HT pickups. Kevin
Thanks Kevin, I had already done a search of fchat and read this, I didn’t have interference with the terminals (luckily!) but I did note the differences. I pulled out the old cap/rotor plus another new spare cap and a complete dizzy from an E-series and compared measurements (4 caps, 2 dizzys, 3 rotors). I have both OEM brown caps and new repro caps. The dimension shown in the sketch from the deck of the dizzy to the internal post which holds the carbon contact were measured. This is the max dimension for the rotor to fit. The distance from the dizzy deck to the contact on the rotor top is 26.9-27.9mm. So the clearance is 2.5-3.8mm from the rotor contact to the post, this seems fine for the stroke of the carbon contact spring (about 4-6mm). The repro caps have a much stiffer spring under the carbon contact compared to the OEM caps and I think this is the problem. A thicker cork gasket would help reduce the spring pressure which I’ll try before attempting to replace the spring. Image Unavailable, Please Login Image Unavailable, Please Login
I ended up pulling the spring and carbon contact out, twist and pull. I shortened the contact a few mm and adjusted the spring, pushed all the way back in and the pressure feels less. Hopefully that’s it, will see in 5k miles.
Sounds like a reasonable solution to me. At least the rotor arm is not a big cost if it still needs replacing .....
