Valve Covers reversed?
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Joined: Sep 2012
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From: Rochester NY
Valve Covers reversed?
Hello,
Does it matter if the valve covers are reversed so that the oil cap/fill is on the opposite side of the engine? I have a 1979 L82 350cc. My oil cap is on the passenger side. I notice other cars have theirs on the driverside. Is mine incorrect? Does it matter?
thanks
Does it matter if the valve covers are reversed so that the oil cap/fill is on the opposite side of the engine? I have a 1979 L82 350cc. My oil cap is on the passenger side. I notice other cars have theirs on the driverside. Is mine incorrect? Does it matter?
thanks
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
If you're running the stock PCV system, it does matter: GM designed the PCV system so that the valve is in the driver's side cover and the breather is on the passenger side very intentionally. It has to do with crankshaft direction of rotation and the natural flow of crankcase gasses within the engine (Duke Williams wrote an excellent description of the system some time ago). Although it does not matter which valve cover has the oil fill cap on it, you should keep the PCV on the driver's side and the breather on the passenger side in order for the PCV system to operate most effectively.
Lars
Lars
Racer
Joined: Mar 2005
Posts: 294
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From: Racine Wisconsin
Probably Doesn't Matter
Lars is correct but I think the question is related only to which side the oil filler cap is on. On my 1970 and 1973 there is a grommet on both valve covers in the same relative location. The location of the oil filler is near the dip stick on the driver's side rear on 1970 and 1973. The PVC is is on driver's side forward. The other grommet (passenger side rear) is a breather (air inlet to balance the PVC) that is connected to the air cleaner base. The grommets are the same size. If the A/C compressor is not installed, the passenger side forward is an easier place to access the oil filler for sure.
Le Mans Master
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Thread Starter
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Joined: Sep 2012
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From: Rochester NY
Photobucket has changed since that pic instructional post was made. There is no IMG box to click on, or at least I can't find it. I see Email, Instant Message, HTML and slideshow, but no IMG.
Is all this really the best system to post pics? Seems other sites allow simple drag and drop. Thanks anyway.
Is all this really the best system to post pics? Seems other sites allow simple drag and drop. Thanks anyway.
Racer
Joined: Oct 2003
Posts: 424
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From: Killeen Texas
If you're running the stock PCV system, it does matter: GM designed the PCV system so that the valve is in the driver's side cover and the breather is on the passenger side very intentionally. It has to do with crankshaft direction of rotation and the natural flow of crankcase gasses within the engine (Duke Williams wrote an excellent description of the system some time ago). Although it does not matter which valve cover has the oil fill cap on it, you should keep the PCV on the driver's side and the breather on the passenger side in order for the PCV system to operate most effectively.
Lars
Lars
Team Owner
Joined: Jan 2006
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From: Crossville TN
In Photobucket, click on the image of the gear in the upper right corner of the photo you want to post. That will display the various filetypes that can be transferred. Go to the last one (IMG) and click on it; that will 'copy' that [IMG] photo file to your clipboard. Now, switch to the CF page, put the cursor in the message box where you want to locate that file and hit CTRL-V to 'paste' it in that post. Done deal.
BTW, the PCV valve will work on either side (air cleaner vent pipe fed to the other cover); but it will work better if the PCV is located on the driver's-side cover.
BTW, the PCV valve will work on either side (air cleaner vent pipe fed to the other cover); but it will work better if the PCV is located on the driver's-side cover.
Last edited by 7T1vette; Oct 31, 2012 at 11:39 PM.
Melting Slicks
Joined: May 2006
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From: Nashville TN
St. Jude Donor '09
In Photobucket, click on the image of the gear in the upper right corner of the photo you want to post. That will display the various filetypes that can be transferred. Go to the last one (IMG) and click on it; that will 'copy' that [IMG] photo file to your clipboard. Now, switch to the CF page, put the cursor in the message box where you want to locate that file and hit CTRL-V to 'paste' it in that post. Done deal.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
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From: Oxford MA-----You just lost the game!!!!
In Photobucket, click on the image of the gear in the upper right corner of the photo you want to post. That will display the various filetypes that can be transferred. Go to the last one (IMG) and click on it; that will 'copy' that [IMG] photo file to your clipboard. Now, switch to the CF page, put the cursor in the message box where you want to locate that file and hit CTRL-V to 'paste' it in that post. Done deal.
BTW, the PCV valve will work on either side (air cleaner vent pipe fed to the other cover); but it will work better if the PCV is located on the driver's-side cover.
BTW, the PCV valve will work on either side (air cleaner vent pipe fed to the other cover); but it will work better if the PCV is located on the driver's-side cover.
Keep the shiny side up!
Scott
Team Owner
Joined: Jan 2006
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From: Crossville TN
I think you would have to have the instrumentation and test cells that GM had in order to measure the difference. But, Lars is correct; it is supposed to work a bit better with the PCV valve in the left-side cover.
Instructor
Joined: Dec 2008
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From: w. jordan utah
covers
thinking about running an old set of holley covers on my 350. the left side has a provision for the pvc and a breather that twists off and is the the oil filler. the right has no holes at all. although there is a spot to drill out. why does it matter which side the breather is on? don't want to drill if its not needed.
Melting Slicks
Joined: Mar 2009
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With PCV and breather on the same side, the crankcase gasses are not removed effectively. PCV sucks out gases but short cycles through the breather rather than drawing the gases out from the pan. The fresh air inlet should be one side of the engine and the PCV should be on the other. Ck. LARS' post above for ideal configuration. mike...
Instructor
Joined: Dec 2008
Posts: 103
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From: w. jordan utah
covers
thanks for the response. i'll drill the other cover , will it matter if i have 2 breathers 1 on each side? i guess i could drill the one and put the pvc in it and run on the left side. but that would leave the right side with a breather and a grommet for ?
Last edited by surfertom; Nov 11, 2012 at 11:29 AM. Reason: more info
Team Owner
Joined: Jan 2006
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From: Crossville TN
The crankshaft rotates in one direction. That rotation creates some turbulence in the space inside the engine. And that causes pressure differentials throughout that space. Apparently, the higher pressure is on the driver's side of that engine block, so putting the PCV valve in the left valve cover will take advantage of a slight increase in airflow through the valve. The effect is small and the difference in PCV function on the basis of one vehicle is insignificant.
Put the [dang] PCV valve on either cover; it will work fine.
Put the [dang] PCV valve on either cover; it will work fine.
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Yeah, the pressure generated in the crankcase has to go up through the lifter valley to get to the valve covers anyway, so I don't see how it could make a whole lot of difference either way. Way back when PCV was first introduced, the PCV valve was on the front of the intake manifold, and the air inlet was at the back, that's why you see old valve covers with no holes in them for any of that stuff. Moving it to the valve covers may have just been a cheaper way to do it, hard to say for sure, I'm not an engineer or anything.
It may make a difference if you have a breather on both sides, the PCV system will draw air through the path of least resistance. It should be set up in such a way that the only air inlet is on the other side of the engine. It shouldn't be hard to find a plug that will fill the extra hole on the valve cover with the PCV valve.
Keep the shiny side up!
Scott
It may make a difference if you have a breather on both sides, the PCV system will draw air through the path of least resistance. It should be set up in such a way that the only air inlet is on the other side of the engine. It shouldn't be hard to find a plug that will fill the extra hole on the valve cover with the PCV valve.
Keep the shiny side up!
Scott