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Old 08-19-2006, 01:12 PM
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PCV ,vacuum questions.

For quiete a while now I have been looking into PCV valves and vacuum questions and came out with theories but nothing sure..maybe someone here could throw in their ideas?
First I have tried reasonning a choice of a pcv valve corresponding to my specific engine wich is a 383 SBC stroker.I have just recently installed one meant for a 1973 corvette L82 equipped.This could be ,in terms of power similar to my 383.I can see there is a letter marked on top of the small counterweight encountered into the said valve wich in this case is a K.I have other valves that are stamped differently: E and F..the K looks a bit heavyer overall.How they work? Is the "bullit" or "counterweight" inside disminish the vacuum by actually staying sit down or pulled up? A heavyer counterweight,submitted to an equal vacuum,would disminish the said vacuum by disminishing the available aperture at the bottom if this is the way they are designed.Oppositely ,a heavyier bullit would allow a greater vacuum to pass freely if the design calls for a disminishing available passage at the top...

Now vacuum strength. My engine shows around 24 inches/hg at around 2,500RPMs I believe this to be very high figure that overcomes the PCV capacities and oil makes its way into the combustion area...my rings are not sat already neither after only 300 miles so I am facing the problem of finding who'S responsible for the oil consumationCV or rings!I don't like the idea of running without the PCV even for experimenting..concerned about blowing seals.

The same engine shows very low vacuum at 650 RPMs idle at around 7-8 inches/HG...I read about this caused by a small advance or wrong valves timing...the timing is around 15 BFTD at this RPM..should I get it up ?

So anybody here who ever diagnosed a PCV valve and could tell me how it does actually stop oil getting sucked-in?


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Old 08-20-2006, 08:36 AM
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Originally Posted by TVR383

So anybody here who ever diagnosed a PCV valve and could tell me how it does actually stop oil getting sucked-in?

If the PCV valve is installed in the valve cover; there should be a baffle at the opening to prevent/reduce oil from being sucked into the PCV valve and then into the intake manifold. The factory baffles in the factory valve covers and some aftermarket covers work well. The aftermarket single plate baffles/diverters do not work as well at higher RPMs. If the PCV valve is installed in the intake manifold rather than the valve cover the single plate/diverter is usually used just below the opening. Since there should be less "splash" of oil in the intake valley area the single plate baffle should work fairly well. I have not tried this method yet. I have not used any of the rubber insert type baffles so can not comment on their effectiveness. Not running a baffle will result in oil being sucked through the PCV valve and into the intake manifold.
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