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i recently installed a catch can on my 97 LS1, looking at different sets of instructions, some say PCV valve before the can, some say valve after the can, which way is right, or does it matter?
I don't think it really matters much if the PCV valve is before or after. Even if it was after the catch can, there will still be some slight oil mist in the vapors as no catch can will separate 100% of the oil out of the crankcase vapors.
As you can see in the Elite Engineering instructions, the placement of the PCV valve depend on if it's an LS1 or LS6.
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Originally Posted by ZeeOSix
I don't think it really matters much if the PCV valve is before or after. Even if it was after the catch can, there will still be some slight oil mist in the vapors as no catch can will separate 100% of the oil out of the crankcase vapors.
As you can see in the Elite Engineering instructions, the placement of the PCV valve depend on if it's an LS1 or LS6.
I would tend to agree with you and as you pointed out EE has the pcv after the can on the LS6 pcv system ('cept for '04). AMW also indicated this manner of installation (after the can) but did not make any references to engine year/type, etc.
I changed my '99 pcv system over to a Z06 style when I did my Z06 intake manifold install a couple years back. I also installed my AMW can on the inside of the R/F frame rails (tilted back about 30-40 degrees).
I would tend to agree with you and as you pointed out EE has the pcv after the can on the LS6 pcv system ('cept for '04).
On the 2004 and on LS1/LS6/LS2 motors it doesn't matter because the "PCV Valve" is really not a valve, but a 2 mm hole in the tube of the valley cover hose nipple.
This is true for the applications ZeeO listed. However, the majority of C5s have a traditional PCV "valve" and since the originator has a 97, the can should me mounted downstream of the PCV valve. While it is true oil aerosols will easily get past a common catch can, a true coalescing filter that is sized correctly will trap more of the airborn oil, due to the much-higher density of its filter element.