Originally Posted By: FetchFar
Originally Posted By: SteveSRT8
The whole reason for valve stem seals is to seal off oil from the rest of the stem, keeping the oil out of the combustion chamber. In a new motor this should be the case, with virtually no oil on the rest of the valve, just the part in the actual valve guide itself.
Some must remain on the valve stem, not perfectly wiped like you claim. As minimal as possible. Its not hard for most people to get.
Originally Posted By: SteveSRT8
PCV is the obvious culprit, and it should be noted that only vapors are transferred there, no carbon or solids of any kind ....
More misinformation from SteveSRT8. Airborne carbon particle soot in small amounts, mixes with oil vapors and travel thru the PCV valves.
Steve stated VIRTUALLY no oil on the rest of the stem, which is in fact the case. The film that makes its way by a seal in good working order is incredibly thin, he did not say it was perfectly wiped.
Also, with respect to solids, anything with a decent air/oil separator should collect most of that, as the product ingested by the PCV system is usually a combination of blow-by gasses, fresh air (ingested through the breather) and oil mist whipped up by the action of the crank, rods, pistons....etc. Most of the oil mist, in a properly designed system, should fall-out/condense in the separator and make its way to the pan. It would be in that mist that any solids would be present (carbon particulate making its way by the rings for example, coke from the ring land area....etc) and in theory, it isn't supposed to make its way into the intake tract.
In application this probably varies wildly manufacturer to manufacturer. In my experience, carbon in the intake tract is usually easily traceable to the EGR valve, engines without EGR or an EGR delete usually get a very light oil film that eventually turns to a bit of varnish in the runners and also usually around the PCV valve area in the valve cover.
