Reading this, I was wondering if using a PCV might reduce lubrication of
the valves over time?
Hope I didn't open up a can a worms here, although I'd like to go
fishing....
On Tue, Feb 7, 2012 at 2:06 PM, Bob Spidell <bspidell@comcast.net> wrote:
> Just when you thought this thread was dead ...
>
> Fired up the BJ8 for a short hop to pick up my uncle on Sunday. Was
> curious, so with the engine running at a fast idle (1,000RPM or so) I took
> the oil filler cap off the valve cover and put my hand over the filler
> hole. I was a bit surprised to find there was fairly significant vacuum,
> enough to seal the palm of my hand over the hole. I've always assumed
> there was enough air leakage to keep the crankcase pressure near
> atmospheric, even with the PCV valve. I'd guess several inches of vacuum
> (if I get ambitious maybe I'll try to get an accurate reading with a
> gauge). There was no difference in idle speed or otherwise with my hand
> over the hole or not.
>
> So, the pseudo-PCV 'system'--with no deliberate fresh air
> source--maintains vacuum in the crankcase and valve cover, instead of
> circulating much air like a true system would (there may be significant
> leakage through the filler cap, though). This is good in that the PCV
> isn't causing the rear cylinders to run lean--would probably have burnt a
> valve by now if it had--and the vacuum probably helps reduce oil
> consumption and leaks.
>
> Can't think of a downside to this, except maybe that not circulating fresh
> air isn't helping control pollution, but then again maybe it is. My oil
> doesn't get very dark, even after 5K miles or so.
>
> Bob
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