Thanks Bonnewagon... Your explanation helps me immensely. I've been trying to solve an oil consumption issue and was suspecting it was due to over ventilation of my PCV system. I've been running a open element type breather filter on one valve cover and the PCV valve to the base of the carb on the other. This seems to be providing too much flow and is allowing oil to be consumed through the intake during highway speeds at higher sustained RPM's. I'm going to try using a closed breather filter with a connection to the air filter and see if that helps balance things out a little better.
Crank Case Ventilation Trouble
- Thread starter FluoFerret
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FluoFerret- You can do that and air will still find it's way inside. The dipstick is a good example. Better that the air is filtered. And remember that under acceleration when there is no manifold vacuum, the crankcase pressure can build and force oil out wherever it can. MadBrax- the PCV valve cover mounted filters are supposed to double as oil separators. That is they have steel wool mesh inside for oil vapors to condense on and drip back into the engine. Pontiac motors mount the PCV in the valley pans which incorporate a baffle for vapors to condense on and also drip back. Both systems are limited and a motor with a lot of blow-by can overwhelm them causing oil to travel past the PCV into the intake manifold. If you mount an air cleaner oil filter and run the valve cover hose to it- check and see how fast it accumulates oil. You may have a tired engine pushing oil. My Bonnewagon has a 20 year old rebuilt 301 engine and I use all the stock items. I don't think I have ever had to clean the little filter in the air cleaner.
Well, try it and see. If it solves the issues then you are all set. If not- further study is indicated. Never be afraid to try things. Even if we make mistakes - we learn.
Bonnewagon, I have an open element breather on the right valve cover and no evidence of oil inside. It was my understanding that this is the fresh air supply that the pcv check valve on the left valve cover is drawing into the engine using manifold vacuum. I have been finding oil in the rubber line between the pcv valve and the carb port. Please correct me if I'm still not getting it but what I've been doing is adding restrictions inside the rubber line, in the last 2 days I've inserted a small section of 3/8" tygon tube into the rubber line. After a couple hundred more miles I added a smaller 1/4" piece of tygon inside the first. My very non scientific experiment has taken place mostly during the return trip home from the last stop of the power tour. I didn't know I had this problem until I spent some time on the interstate driving at highway speeds and that's the only time I have the problem. It appears that I have reduced the oil consumption but again it is a very non scientific experiment. I was hoping that replacing the open element breather with a closed breather ported to the air cleaner would result in a reduced flow through the engine at high throttle and during highway cruising. I hope this isn't coming across as me just rambling, I feel like I may be doing just that. Please correct me if I'm way far off from where I should be.
Oh, and at the risk of more rambling. I have tall edelbrock valve covers and I'm guessing that we could also question the baffling within those.
Oh, and at the risk of more rambling. I have tall edelbrock valve covers and I'm guessing that we could also question the baffling within those.
MadBrax- yes, you are correct. With a PCV valve in one valve cover and a breather in the other you have an open system. The manifold vacuum draws blow-by vapors through the PCV valve and the open breather allows fresh air into the engine. However at low vacuum there is hardly any flow and if any pressure builds it goes out the open breather. The closed system with a hose to the air cleaner then takes over because at low vacuum you have high airflow through the carburetor. The reason you have oil in the PCV hose is because it is getting there either by very oily vapors or being flung there by the valve train. Ever try to adjust rocker arms with the engine running? Oil goes everywhere. You may even have a push rod squirting oil right at the PCV valve. Most stock valve covers have a baffle plate inside covering the PCV valve grommet hole if that is where it is mounted. I don't expect aftermarket brands to consider that. Putting restrictions in your hose is treating the symptoms and not the problem. If it reduces the oil it is because you are restricting the vapor flow and giving the oil something to stall against. But by doing that you are defeating the purpose of the PCV valve. I would try and figure out where the oil is coming from. If the valve train is flinging oil perhaps if you epoxied a baffle to the inside of the valve cover it would stop it. Then you would know for sure.
Cool, Thanks for your patience helping me understand this. There is a plate directly under the hole for the pcv valve but I don't know the shape, size, or anything beyond that. I'll now be removing the inline resistors I've added and focus my non scientific experimentation inside the valve cover.
Learned something new today, Thanks again..
Learned something new today, Thanks again..
Concerning the oil in the PCV-System, created by oil-vapors, I got rid of that when I first installed an oil-temperature gauge, and then, an external oil cooler. my engine, even though the water temperature was always perfect, had an oil temperature of far over 250°F (beyond the gauges reading). the oil was able to handle these high temps but the catch can always had about 4 spoons of oil per refuel stop. with the external oil cooler i brought it down to a cosy 180-200°F. engine runs a lot smoother now, hardly any oil in the catch can, and a clean pcv-valve...
That makes a lot of sense. High oil temps would vaporize more oil than normal and thin it out. What kind of catch-can are you using?
This may also be part of the problem. I just added AC and thought it would be a good idea to add an electric fan in front of the condenser. Turns out it's just blocking airflow to the radiator. My highway water temps are 200-210 vs 180-190 off highway. I can only imagine what the oil temps are.. Yes, I will be removing the electric fan from the condenser.
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