Alrighty then..
Pics ain't great but 3 items, 1 bottle of Rit black liquid dye. I didn't bother dismantling the oil cap, just wrapped some wire around the 'neck' and suspended it so the appropriate parts were just below the water surface..

Bring a pan of water to just below a simmer, add some dye, add the parts, wait an hour..
2 out of 3 ain't bad


