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I have searched the internet low and high, and it seems everyone has a different opinion or way of doing this. I have a newly acquired c4 corvette with a stroker ls6 swap. I am going over all of the previous owners work and the PCV system has got me stumped. No matter where I look online, I can not seem to find any definite answers, so any help would be appreciated.
As the car sits, it seems the only 'PCV' system is between the two valve covers, with a catch can in the middle. Something about this doesn't seem right to me. I only have the pictures attached, as I am away from my car currently.
Also, the oil fill cap adapter that connects to the catch can is loose. I have taken it off and inspected it multiple times and it never seems to 'lock' into place, is this a concern? It just sort of screws in enough to not pop off but still wiggles quite a bit, making me wonder if pressure is escaping through here.
Please let me know if there are any questions or anything I can clarify more.
I need some help with my PCV system setup. Recently acquired a c4 corvette with an ls6 stroker swap and I am slowly going over the old owners work. I’ve come to the PCV setup and it does not make sense to me.
Everywhere I look online, it seems there are different opinions on how to have this set up. The correct set up on the car is just a line run from one valve cover to the next with a catch can in line. Something about this seems off. Please let me know if it should be changed or re routed.
Also… the oil fill cap adapter, that goes directly to the catch can is loose. I’ve taken it off to inspect it and have tried tightening it back on and it never gets more than “snug” at best. It still wiggles and just kind of sits there, with just enough thread to keep it from popping off. Is this normal? Or could this cause a leak in the PCV system.
I will attach pictures ( they are the only pictures I have currently as I am away from my car)
having recently dug around to solidify my own weird LS Corvette catch can routing, what i can offer is that your setup is nothing like an LS6.
typical LS6 uses a air:oil separator in the valley cover that had a dirty exit pipe on the passenger side between the throttle body & the steam line. that would loop immediately back up to the intake manifold for a constant vacuum source (catch cans are normally inserted in-line here to filter that oily air before returning to be burned). the passenger valve cover drew fresh air from the throttle body into the crankcase via a barb between the #2 & #4 fuel injectors. the driver's valve cover had a filler plug to cap off the usual PCV valve spot.
since your car clearly replaced that driver's side plug with a PCV valve (like a late LS1), that should be the dirty line connected to your catch can input. it also appears that the oil cap line (which, yes - should be tight to preclude leaks... maybe try a thicker o-ring) might also be a dirty PCV outlet going into your catch can instead of a clean return to the intake tract. those mighty mouse cans have a flap inside the top filter that seals during vacuum but allows positive pressure to escape (keeps from introducing unmetered air).
that said, it appears he may have changed to an early LS1 valley cover (sans PCV separator) plus late LS1 valve covers (early had a passenger-rear dirty barb that y-piped with the driver's side into a PCV valve). your lines look to modify the routing to make all ports dirty & vent pressure to atmosphere instead of having dirty / clean sides that circulate.
PS: LS1 / LS6 engines (1997-2005) had at least three different factory PCV configurations, so anybody that posts how-to info that doesn't specify which version (or says it applies to them all) is being ignorant and making people's lives miserable.
what i don't see is a vacuum source from either the intake manifold, throttle body, or air bridge... not saying they don't exist, but i can't tell in those pics. i also can't see what the passenger valve cover front barb is connected to.
if there's no vacuum source drawing PCV vapors out, then it's only venting via the pressure of the blow-by (instead of using circulation or keeping the case under vacuum).
Oil cap adapter line is definitely some extra that's not needed.
Doesn't look like you have the vented Valley Cover so I'd be setting it up to have the PCV Valve in line somewhere to the Catch Can then to Intake Vacuum. Passenger side TB Port is the clean air in going to the passenger side Valve Cover.
I think you are correct. I also do not seem to see a vacuum source. It appears the throttle body port was removed and plugged, and the port to the intake manifold is also capped (see picture, appears to be a rubber cap with a worm clamp).
I would agree with what you are suggesting, that it seems my set up is all ports dirty / vent pressure to atmosphere. Unfortunately like I said I’m away from my car right now and probably won’t be able to take a look closer until tomorrow or Saturday, but it definitely raised a red flag when I was looking at this. You can see the circled rubber cap on the intake manifold port. And if you look closely here, it looks like the breather on the throttle body was removed as well and plugged…
Oil cap adapter line is definitely some extra that's not needed.
Doesn't look like you have the vented Valley Cover so I'd be setting it up to have the PCV Valve in line somewhere to the Catch Can then to Intake Vacuum. Passenger side TB Port is the clean air in going to the passenger side Valve Cover.
So do you suggest the current setup from the drivers side valve cover, to the catch can, then to the intake manifold? I don't see a port on my throttle body to connect to the passenger valve cover.
Not at all and that is subject to debate... I don't really want to get into what the consequences are from running a PCV system verses ventilating blowby to atmosphere but I'll just say that ALL emissions controlled vehicles are required by law to run PCV.. I'll also add that some laws made in this country "mainly traffic laws" were made to be broken otherwise they couldn't fine you for it.
Not at all and that is subject to debate... I don't really want to get into what the consequences are from running a PCV system verses ventilating blowby to atmosphere but I'll just say that ALL emissions controlled vehicles are required by law to run PCV.. I'll also add that some laws made in this country "mainly traffic laws" were made to be broken otherwise they couldn't fine you for it.
okay I gotcha, appreciate the input. Definitely still going to take a look at all of the ports on the engine and figure out what’s what. At the very least I can clean up the current setup and short the lines quite a bit
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PCV System Help 
PCV System help 
