PCV and an LT4 Manifold... wheres it going?
05-07-2008, 11:11 PM
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PCV and an LT4 Manifold... wheres it going? Ok I have a thread about oil in my intake manifold and its not coming through the TB this leaves the PCV.
Now I have a car with an LT4 conversion rebuild however you want to word it (It was rebuilt less then 3000 miles ago).
Now I have oil inside my intake manifold. I just used a whole can of carb cleaner cleaning it all out of the intake manifold and now I am letting it dry over night.
Either way I can def say the trail of oil leads from the pcv that goes straight into the middle of the intake manifold and the line goes to the drivers side center where the PCV Check Valve actually is... so where the hell is the oil coming from?
I have been spraying in the manifold trying to clean it but now I am worried I may have mixed carb cleaner and oil in my motor somehow... since oil has to run through there somewhere but where? Is there oil below the runners in the middle of the intake manifold? I have no idea honestly and really need the help here.
This is under the TB the hole goes in to the IM directly not where the PCV Check valve is. I sprayed the tip and may have gotten some carb cleaner in there while cleaning that and the area so half of me is tempted to drain the oil and refill it.... but first I want to know how oil is run through the intake manifold since this line goes from the front under the TB to the side with the PCV Check Valve.... a diagram would rock but basically whats going on here?
Now I have a car with an LT4 conversion rebuild however you want to word it (It was rebuilt less then 3000 miles ago).
Now I have oil inside my intake manifold. I just used a whole can of carb cleaner cleaning it all out of the intake manifold and now I am letting it dry over night.
Either way I can def say the trail of oil leads from the pcv that goes straight into the middle of the intake manifold and the line goes to the drivers side center where the PCV Check Valve actually is... so where the hell is the oil coming from?
I have been spraying in the manifold trying to clean it but now I am worried I may have mixed carb cleaner and oil in my motor somehow... since oil has to run through there somewhere but where? Is there oil below the runners in the middle of the intake manifold? I have no idea honestly and really need the help here.
This is under the TB the hole goes in to the IM directly not where the PCV Check valve is. I sprayed the tip and may have gotten some carb cleaner in there while cleaning that and the area so half of me is tempted to drain the oil and refill it.... but first I want to know how oil is run through the intake manifold since this line goes from the front under the TB to the side with the PCV Check Valve.... a diagram would rock but basically whats going on here?
05-07-2008, 11:40 PM
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Your PCV check valve is not plumbed into the plenum. The only way oil can be getting into your plenum is through the breather tube (tube connected between your valve cover and throttle body) which is a common problem on the LTx engine.
All the vacuum ports on the manifold get their vacuum from internal ports that run along the bottom of the intake runners including the PCV vacuum. The PCV valve port is plumbed into the bottom of the intake on the oil valley side.
All the vacuum ports on the manifold get their vacuum from internal ports that run along the bottom of the intake runners including the PCV vacuum. The PCV valve port is plumbed into the bottom of the intake on the oil valley side.
05-07-2008, 11:45 PM
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Ok well I def checked the TB I have it off there is no oil coming through there. All the hose and inlets are dry and pulling it apart for the new Holley I am putting on its def dry inside.
Now the oil valley... thats under the TB that center port.... how worried should I be that I sprayed Carb cleaner all around that and it seems to me the IM also has holes going down there... is that direct access to my oil in which case I just sprayed carb cleaner all over it which means I should be worried....
Either way if this is where the line goes can I cap it since I have breathers? I plan on staying NA and honestly it goes directly from the IM below the TB to the drivers middle of the IM with the PCV Check Valve there... I do not see how its doing anything other then sucking oil in which is driving me nuts and now I have effectively caused myself another problem it looks like....
Now the oil valley... thats under the TB that center port.... how worried should I be that I sprayed Carb cleaner all around that and it seems to me the IM also has holes going down there... is that direct access to my oil in which case I just sprayed carb cleaner all over it which means I should be worried....
Either way if this is where the line goes can I cap it since I have breathers? I plan on staying NA and honestly it goes directly from the IM below the TB to the drivers middle of the IM with the PCV Check Valve there... I do not see how its doing anything other then sucking oil in which is driving me nuts and now I have effectively caused myself another problem it looks like....
05-08-2008, 12:14 AM
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I'm going to have to look at the spare intake I have now. The port underneath the TB is a vacuum port for the PCV (depending on year), but now that I think about it, it may be plumbed into the plenum instead of the intake runners and could be a way for oil to get into the plenum as well.
Don't worry about the carb cleaner. That **** evaporates lickety split. There are threads floating around somewhere on cz28.com and maybe other ltx boards where people have used catch cans for both the breather tube and the pcv valve lines.
Don't worry about the carb cleaner. That **** evaporates lickety split. There are threads floating around somewhere on cz28.com and maybe other ltx boards where people have used catch cans for both the breather tube and the pcv valve lines.
05-08-2008, 12:18 AM
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Thanks for the help.. I am worried that it may have gummed things up but your right it does evap quickly.... Just hope I do not see any problems... thats the last thing I want to see from trying to clean things.
Let me know what you find out, I def want to figure out where this oil is getting in.... I guess a picture of the bottom of an LT4 Intake Manifold would be a huge help... I want to know if those holes right at the front (The one in the middle of the TB and the 2 right next to it looking inside the intake manifold) lead down to where oil is or if that line at the bottom below the TB is the only access to oil possible and even then how that line gains access to oil.
I am def changing my PCV but at this point I am not sure if I should reconnect it or not....
Let me know what you find out, I def want to figure out where this oil is getting in.... I guess a picture of the bottom of an LT4 Intake Manifold would be a huge help... I want to know if those holes right at the front (The one in the middle of the TB and the 2 right next to it looking inside the intake manifold) lead down to where oil is or if that line at the bottom below the TB is the only access to oil possible and even then how that line gains access to oil.
I am def changing my PCV but at this point I am not sure if I should reconnect it or not....
05-08-2008, 12:52 AM
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The only line that is plumbed into the oil valley is where your PCV valve mounts on the side of the intake. All others are vacuum ports w/in the intake. I'll see what I can find out later this morning. I assume you have a vented opti?
05-08-2008, 01:36 AM
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Yes so far as I know. (On the Opti Question)\
So your saying that where the PCV Valve (The actual Check Valve on the drivers side in the middle of the IM) is, is the only spot where oil joins the intake manifold? I only see a hole for it to plug in nothing about oil that I can tell....
Something tells me mine is very oddly setup now...
So your saying that where the PCV Valve (The actual Check Valve on the drivers side in the middle of the IM) is, is the only spot where oil joins the intake manifold? I only see a hole for it to plug in nothing about oil that I can tell....
Something tells me mine is very oddly setup now...
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05-08-2008, 06:16 AM
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The passage where the PCV valve seats is routed to the underside of the intake. On the underside of the intake you will find a large baffle bolted to the intake. That baffle is to keep oil from having a direct route through your PCV valve and hose.
That passage and your breather tube are the only sources of where oil can get into the plenum either by entering through the PCV vacuum port or through the TB via breather tube.
I just took a look at my spare manifold and yes there are two large ports just on the other side of the plenum wall where the PCV system primarily gets its vacuum. So if youre breather hose is dry the only other way it could be coming in is through your PCV vacuum port. Again... very common for the LT1.
The reason why I asked about the opti is because most commonly you'll find vented optis will have the PCV vacuum hose under the TB where on non-vented optis there will be a U-shaped hose on the drivers side of the intake. That hose is uses the same vacuum port that a vented opti uses.
That passage and your breather tube are the only sources of where oil can get into the plenum either by entering through the PCV vacuum port or through the TB via breather tube.
I just took a look at my spare manifold and yes there are two large ports just on the other side of the plenum wall where the PCV system primarily gets its vacuum. So if youre breather hose is dry the only other way it could be coming in is through your PCV vacuum port. Again... very common for the LT1.
The reason why I asked about the opti is because most commonly you'll find vented optis will have the PCV vacuum hose under the TB where on non-vented optis there will be a U-shaped hose on the drivers side of the intake. That hose is uses the same vacuum port that a vented opti uses.
Last edited by SS RRR; 05-08-2008 at 06:25 AM.
05-08-2008, 01:03 PM
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So would it be safer to just plug the PCV Check Valve port and the Stem Port below the TB? Seems to be the safest answer to me.
I need to stop this oil getting into the intake manifold... and I am at a loss for how to do so. I can try a new PCV Valve but I do not think thats going to do it.
I need to stop this oil getting into the intake manifold... and I am at a loss for how to do so. I can try a new PCV Valve but I do not think thats going to do it.
05-08-2008, 08:01 PM
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The only way to get around it is to plug off your PCV system and use a breather. If the car needs e-check or visual inspection though you'll fail since that is not exactly environmentally friendly. Or, as already stated you can get a catch can for the PCV hose and breather tube...
It's just another one of those imperfection things about the LT1...
It's just another one of those imperfection things about the LT1...
05-08-2008, 08:31 PM
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I ordered a catch can and bought a new PCV. I have breathers already but that seems to be the best way. I could care less about being friendly... I am removing the cats, air and egr anyway lol.
