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If you’re having trouble getting a stable idle try pulling and plugging the PCV line.
There are a couple of solutions for high performance camshaft situations where you have to or want to run a PCV system. There are charts available that give valves for different idle vacuum operations or you can spend your money on an adjustable PCV valve like these Dual Flow Adjustable PCV Valve – M/E Wagner Performance Products.

Norm
 

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I've asked these kind of questions about PCV before and am still a little mystified about the flow process. I don't understand how the 'other side', which usually consists of a tube going in to the air cleaner area (after the MAF, if that's what you have) is any different than an unmetered source of air. It does allow for excess crankcase pressure to flow into the intake stream (metered) when high rpm operation produces excess crankcase gases but when the engine is making strong vacuum, isn't it just an open tube from the valve cover ported into the air cleaner area? I don't think the pressure in the air cleaner area is any more than atmospheric, so isn't it more or less the same as having an open breather on the other side? I hope I'm not hijacking this thread!?

I can clarify a couple things I've learned about the PCV:

1.) Sealed does not mean airtight. If you don't allow for excess crankcase gases to vent at high rpm (when the pcv spring is forcing it closed), you will end up with an oil leak. Simply putting an airtight cap on one valve cover and a pcv on the other isn't the answer. You need to ensure the other side allows for the exit of excess crankcase gases (my question above revolves around how those gases are dealt with). This may seem obvious to some but it took a real world experiment to show me that SEALING one valve cover with a pcv on the other side doesn't work.

2.) Not all filtered breathers are created equal. I tried a pcv on one side and filtered breather that looked like a mini air cleaner on one side and struggled to get the tune right on my mass air engine. I tried a denser, foam-filled breather instead and it made the engine much happier. I have always supposed that it flows LESS than the mini air cleaner breather and so has less of an impact on my tune. I settled on this combination because the placement of my MAF sensor makes returning crankcase gases to the air cleaner area problematic.

EDIT: I don't want anyone to presume I'm distributing expertise. I am NO expert, just sharing what I've discovered and trying to learn myself as well.

Sean
 

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Discussion Starter #23
I've asked these kind of questions about PCV before and am still a little mystified about the flow process. I don't understand how the 'other side', which usually consists of a tube going in to the air cleaner area (after the MAF, if that's what you have) is any different than an unmetered source of air. It does allow for excess crankcase pressure to flow into the intake stream (metered) when high rpm operation produces excess crankcase gases but when the engine is making strong vacuum, isn't it just an open tube from the valve cover ported into the air cleaner area? I don't think the pressure in the air cleaner area is any more than atmospheric, so isn't it more or less the same as having an open breather on the other side? I hope I'm not hijacking this thread!?

I can clarify a couple things I've learned about the PCV:

1.) Sealed does not mean airtight. If you don't allow for excess crankcase gases to vent at high rpm (when the pcv spring is forcing it closed), you will end up with an oil leak. Simply putting an airtight cap on one valve cover and a pcv on the other isn't the answer. You need to ensure the other side allows for the exit of excess crankcase gases (my question above revolves around how those gases are dealt with). This may seem obvious to some but it took a real world experiment to show me that SEALING one valve cover with a pcv on the other side doesn't work.

2.) Not all filtered breathers are created equal. I tried a pcv on one side and filtered breather that looked like a mini air cleaner on one side and struggled to get the tune right on my mass air engine. I tried a denser, foam-filled breather instead and it made the engine much happier. I have always supposed that it flows LESS than the mini air cleaner breather and so has less of an impact on my tune. I settled on this combination because the placement of my MAF sensor makes returning crankcase gases to the air cleaner area problematic.

EDIT: I don't want anyone to presume I'm distributing expertise. I am NO expert, just sharing what I've discovered and trying to learn myself as well.

Sean
thanks sean
I settled for a PVC valve on the PS intake cover connected to vacuum from my FiTech throttle body. On the DS intake cover, I'm using a K&N "mini air filter" push in. I figured this is no different than hooking a vented breather up to my air cleaner. I'm assuming the EFI will learn and tune accordingly.
 

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2.) Not all filtered breathers are created equal. I tried a pcv on one side and filtered breather that looked like a mini air cleaner on one side and struggled to get the tune right on my mass air engine. I tried a denser, foam-filled breather instead and it made the engine much happier. I have always supposed that it flows LESS than the mini air cleaner breather and so has less of an impact on my tune. I settled on this combination because the placement of my MAF sensor makes returning crankcase gases to the air cleaner area problematic.
Sean, when the breather is connected after the MAF the air drawn through the engine by the PCV valve is metered and thus compensated for by the ECM. Using an open breather results in unmetered air entering the system and that is probably what messed with your tune. The breather line to the air cleaner will only rarely act as a pressure vent. Wide open throttle is one possibility as well as an extremely worn or damaged engine. At wide open throttle the blow by gasses entering via the breather line, on a reasonably sound engine, will be a very small percentage of the air flow and will not mess with the tune.
Glad you found a combination of breather type and PCV valve that works for you.
 
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