I think its a good preventative measure to have a check valve installed...Also I always make sure that all vacuum, boost, and breather lines are clamped.....
I'll be installing a 1/2" Boomba check valve later this morning...I just didn't have time to finish up last night after installing the OCC...
The JLT OCC is airtight and sealed very well by design so my concern was not with creating any potential boost or vacuum leaks...However, there are 2 other reasons as to why I don't want boost pressure directed towards and filling up the catch can.....
1) Reason why I don't want to have the OCC pressurized during high boost conditions (particularly important when the can begins to fillup with blow-by residue) is that having the check valve in place will prevent oil that has accumulated in the OCC from "percolating" and splashing about during high turbulent conditions within the can occurring during quick boost spooling which can create quite a mess internally by stirring up the heavier "sludge" that has already collected on the bottom of the can...I really don't want to chance having any residue or crap that the can had collected getting all over and gunking up the internal upper mesh filter and then having it pushed back towards the PCV...
2) Installing a check valve between OCC outlet port and IM (located closer to intake manifold port) essentially will block or cap off the IM port during boost conditions...There is no advantage in having high boost pressure directed towards and filling up an empty canister or chamber (OCC) from the IM during boost spool-up ... Also there is no need to pressurize more volume than needed in the intake manifold!
Boomba Check Valve:
http://www.boombaracing.com/check-valve-12-mm-1-2/
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Installed:
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