I just now got around to cleaning the parts for a spare 13B I have in my shed (Series 4 NA). Bought it disassembled from a guy who was parting out a car he purchased, unknown if it was the original engine but the shell was rough and had a fair bit of mileage.

Cleaned it up, and this engine is definitely not original. The apex seals are worn, and the irons have slight wear in the usual places, but the rotors and housings are basically brand new. While there was carbon on the rotors it was just a skim coating, and I was able to remove almost all of it with just a toothbrush and degreaser. The engine was dirtier on the outside than on the inside.

The rotors are so new that they still have the original cadmium coating on them, and appear almost completely unworn. I was curious to see if anyone had experience as to how long that coating lasts, as that would tell me roughly what the mileage is. Regardless of mileage I lucked out here, but it would be good to know.

To give an idea of how they look, the coating is only slightly duller and rougher than the coating on Aaroncake's RX-5 rotors in his YouTube series (episode 4).

 

First of all I want to say Cadmium is really toxic heavy metal similar to lead (but isn't lead - I hope that makes sense). The coating is applied by electroplating which is a micro version of welding and will last forever if left to sit there.

Hope that helps.

 

I was actually referring to how long it lasts when run inside an engine, but that is helpful. Thanks for the information. I know that if it sits on a shelf the coating will last forever, but most of the time when I see pictures of used rotors the coating is gone or almost gone. Sometimes people scrub it off when cleaning by accident, but I think it often just wears away through use and exposes the cast iron underneath. That's why I was curious to see if anyone knew roughly speaking how high the mileage on an engine has to be for the coating to have worn off. Any evidence stated would be purely anecdotal, but it would be interesting to know roughly what mileage it is.

 

it gets covered in carbon as soon as you start the engine, so it lasts forever.