trikerbob Posted December 27, 2006 Share Posted December 27, 2006 Hi guys, I'm getting my EA82 ready for my Trike and so far I've removed all the smog stuff and installed a new Weber 32/36 Carb. I just today finished all that and have been hooking up breather hoses from the valve covers to each other and into the base of the air cleaner of the carb. One thing I did that I'm not real sure was a good idea or not was that I just pluged off the PCV valve on the back of the manafold just below the carb. I've always considered that item as part of the smog stuff and was not even on early motors. Since I have basicly converted this motor back to a pretty basic carbed motor without all the smog stuff, I can't help but wonder why I would need that valve. I know the motor must breath and I know thats where the openings in the valve covers come from. Won't they be enough, or is the extra suckion of the PCV valve coming off the intake manafold needed? I would hope to get more than just a couple opinions about this. I'd like some solid knowledgeable information about if this is ok or if its a bad idea. Thanks, Bob Link to comment Share on other sites More sharing options...
mikeshoup Posted December 27, 2006 Share Posted December 27, 2006 Originally, the engine vented its crankcase gases back into the intake. The PCV valve is a one way valve, and simply controlled when the gases were vented, and prevented the gases from going the wrong way. You can just plug the PCV valve and put breather(s) on the valve covers. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 27, 2006 Share Posted December 27, 2006 Yeah - just as long as you use some filters on the valve cover breather tubes you'll be fine. The PCV, besides being useful for emissions, is also very useful when "sealing" an engine against weather intrusion. Having the valve covers loop back to the intake with a one way check valve is the most appropriate solution if you are putting on a snorkel, and are going through some deep puddles. For trike I can't see this being an issue though. Just thought I would toss that out in case anyone reads this and thinks it's ok to get some bling "V8" style mini-filters for his valve covers and then go hit the deep stuff. GD Link to comment Share on other sites More sharing options...
nipper Posted December 27, 2006 Share Posted December 27, 2006 http://en.wikipedia.org/wiki/PCV_valve NEVER plug a pcv valve. Engines were never totally sealed, they used to be vented to the atmosphere. Now they are vented to the manifold. nipper Link to comment Share on other sites More sharing options...
mikeshoup Posted December 27, 2006 Share Posted December 27, 2006 Curious, why would just plugging the PCV valve and connecting the valve covers to a breather filter be a problem? Link to comment Share on other sites More sharing options...
nipper Posted December 27, 2006 Share Posted December 27, 2006 Curious, why would just plugging the PCV valve and connecting the valve covers to a breather filter be a problem? Bcause as the car cools down, it wil draw fresh air into the cankase. There is humidity in the air, and water and oil dont mix well, especially if you drive lots of short trips. Also you will fail inspection if you have emissions. nipper Link to comment Share on other sites More sharing options...
mikeshoup Posted December 27, 2006 Share Posted December 27, 2006 Wouldn't that be the case though with the PCV system in the intake? The air the engine breathes in is the same air as the air outside, so I would think there would be just as much humidity in the air tube as there would be outside it... Link to comment Share on other sites More sharing options...
nipper Posted December 27, 2006 Share Posted December 27, 2006 PCV = Postive Crankase Ventilation Valve. It is a one way valve. When there is positive pressure in the crankase, the blowby flows out into the the manifold or air cleaner. When the engine is off, the valve seals so no outside air can get in the crankase. What is the point of plugging it anyway? it does no harm and robs you of no power. If anything it helps add time to the life of an engine. nipper Link to comment Share on other sites More sharing options...
mikeshoup Posted December 27, 2006 Share Posted December 27, 2006 Scratch the old post. Still doesn't make sense to me. Just because the valve is sealed, doesn't mean the valve covers are sealed. I would still think the valve covers would suck in air as the engine cooled. Link to comment Share on other sites More sharing options...
nipper Posted December 27, 2006 Share Posted December 27, 2006 So can one still have the PCV valve in place and vent to the atmosphere? Makes sense to me now. PCV is the vent to the atmosphere, but only when the engine is running. And since the engine is a huge air pump the cankase gasses get drawn into the engine and burned. nipper Link to comment Share on other sites More sharing options...
mikeshoup Posted December 27, 2006 Share Posted December 27, 2006 I edited my old post too late. I'm still confused though. Just because the PCV valve is closed, doesn't mean the valve covers still won't suck in air using the original setup, as the valve covers are still open. Am I missing something? Link to comment Share on other sites More sharing options...
nipper Posted December 27, 2006 Share Posted December 27, 2006 I edited my old post too late. I'm still confused though. Just because the PCV valve is closed, doesn't mean the valve covers still won't suck in air using the original setup, as the valve covers are still open. Am I missing something? Yes you are missing something. The part about the engine being off. The pcv valve is weighted so it closes when there is no pressure to open the valve. Didnt wikipedia make any sense? nipper Link to comment Share on other sites More sharing options...
mikeshoup Posted December 28, 2006 Share Posted December 28, 2006 This is getting quite long here... I'm terrible at hijacking threads, aren't I? So now, because the PCV valve is closed, wouldn't that be the same as plugging the PCV valve? I agree that as the engine cools down, it will suck air in through the valve covers. How does the PCV valve seal the valve covers though? I could see this instance on an engine like my old toyota where the only vent was the PCV valve. Though on our Subarus, you have the valve covers as well, and I don't see how the PCV valve closing seals those off, or if it does, how this is any different than plugging the PCV valve closed permanently. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 I see what nipper is driving at, but really, a bit of condensate inside an engine that is run regularly, or garaged should not make any difference. 180 degree engine temp will drive out any small amounts of condensate rather quickly once the engine reaches operating temp. Also, condensation will genererally collect on the filter element, and not actually make it inside the engine. As a theory, I see what you are driving at, but for a garaged Trike in CA, I can't possibly see this being a problem in practice. Also, I am pretty sure emmissions aren't going to matter for him either. Also, since I'm a really lazy gbastard, the valve cover hoses on my sedan have been OPEN (no filter at all, and no PCV valve connection) for the last 15,000 miles, and I've changed the oil 4 times so far and there is NO evidence of any contamination in the valve covers or anywhere else. And the car is outside all the time, and I live in a wet, wet climate. GD Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 This is getting quite long here... I'm terrible at hijacking threads, aren't I? So now, because the PCV valve is closed, wouldn't that be the same as plugging the PCV valve? I agree that as the engine cools down, it will suck air in through the valve covers. How does the PCV valve seal the valve covers though? I could see this instance on an engine like my old toyota where the only vent was the PCV valve. Though on our Subarus, you have the valve covers as well, and I don't see how the PCV valve closing seals those off, or if it does, how this is any different than plugging the PCV valve closed permanently. re re re re read what ive been saying. Or i dont know what your saying. the pcv valve is closed when the engine is off. the valve is open when the engine is running. This draws out unburnt gasses and keeps the pressure from building up and causing leaks. Breather tubes, pcv valves, breathers all come from the valve covers . They come from the highest point to remove the gasses. As an engine runs, the crankcase (containing the crankshaft and other parts) begins to collect combustion chamber gases which leak past the rings surrounding pistons and sealing them the to the cylinder walls. These combustion gases are sometimes referred to as "blow by" because the combustion pressure "blows" them "by" the pistons. These gases contain compounds harmful to an engine, particularly hydrocarbons, which are just unburned fuel, as well as carbon dioxide. It also contains a significant amount of water vapor. If allowed to remain in the crankcase, or become too concentrated, the harmful compounds begin to condense out of the air within the crankcase and form corrosive acids and sludge on the engine's interior surfaces. This can harm the engine as it tends to clog small inner passages, causing overheating, poor lubrication, and high emissions levels. To keep the crankcase air as clean as possible, some sort of ventilation system must be present. Link to comment Share on other sites More sharing options...
WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 #1 The PCV system is the replacement for the road draft tube system. The old Worthington I worked on had a 2" dia tube with mesh on the end that ran down the side of the block and stopped below the bellhousing. It had a breather filter on the front of the block. The way this system worked was that as the truck drove forward, air would flow past the end of the road draft tube, and suck crankcase air out. The only drawback other than emissions wise, was that the oil suspended in the air was spread on the road. Great for dirt roads, not so good for paved ones. #2 The PCV system uses controled manifold vacuum to suck the crankcase air into the intake. It's then burned, eliminating the slime on the middle of the road left by the road draft system. A small filter on the valvecover lets air in, and bad air is sucked into the manifold. The 71 Ford bronco of my uncles has this version. #3 The "closed" PCV system uses an inlet from the air intake tract, pre throtle but post air filter. The rest of the system is the same as #2 The reason behind a system which premotes flow though the crankcase is that all engines have blowby. Blowby is acidic, contains moisture, and can sometimes be flammable. Having flamable, acidic gasses in your crankcase isn't a good thing. None of the subaru engines was designed with a road draft tube to suck out the gasses, so you have to keep at least the suction side of the PCV system. Feel free to put a couple small filters on each valvecover, but keep a pipe running from the block to the PCV valve and to the manifold. It's harldy complicated, or detrimental to the engines performance. Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 I see what nipper is driving at, but really, a bit of condensate inside an engine that is run regularly, or garaged should not make any difference. 180 degree engine temp will drive out any small amounts of condensate rather quickly once the engine reaches operating temp. Also, condensation will genererally collect on the filter element, and not actually make it inside the engine. As a theory, I see what you are driving at, but for a garaged Trike in CA, I can't possibly see this being a problem in practice. Also, I am pretty sure emmissions aren't going to matter for him either. GD Emissions will matter if he fails the visual test. Also if he drives short drives where the engine never warms up, condenstaion will matter. Weather the car is garaged or not, moisture is moisture and its in the air if the system is wide open. nipper Link to comment Share on other sites More sharing options...
WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 The least of the worrys is emissions. It's a system which reduces acid in the oil, rusting in the block, and if its blocked off, positive pressure in the crankcase forcing oil through the seals. And if you get an explosive mix in the block, the backfire could blow more than seals out. Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 The least of the worrys is emissions. It's a system which reduces acid in the oil, rusting in the block, and if its blocked off, positive pressure in the crankcase forcing oil through the seals. And if you get an explosive mix in the block, the backfire could blow more than seals out. hehehe backfires made life exciting Another thing that people forget. All these little systems have helped add longetivity to engines. In the 1950's 60,000 miles was considered high, now 150,000 is high, and higher for our subarus. It doesnt take much to contaminate oil. Some moisture may sound insignificant, but get a little water in the wrong place and damage can happen. Superior fuel control, better oils, a tighter oiling system all help in this process. PCV valve has been around since 1955. http://people.ucsc.edu/~kbrandt/mustang/smog.shtml nipper Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 As a custom trike, I doubt he has to pass any inspections. The moisture thing just doesn't seem to be a problem in practice. If you were only taking short trips all the time there are many other problems that would get the engine before a bit of condensation would - especially with regular bi-monthly oil changes, which would be required for a vehicle with that sort of usage pattern. As for it "needing" the suction of the intake, the pumping action of the pistons creates a positive flow of air in and out of the breather tubes on the valve covers. I once put a rag over the breather tubes as a makeshift filter, but the backpressure was too great, and the poorly fitting drivers side cam seal was pushed out of the block creating a HUGE oil leak. Put your hand up to the breather tube sometime, and you'll see what I mean. Perhaps it's the opposed cylinder oreintation that creates this flow effect, but at any rate, manifold vacuum is not needed to "pull" the gasses out - they will evacuate on their own provided the the breather tubes are not blocked. GD Link to comment Share on other sites More sharing options...
WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 , but at any rate, manifold vacuum is not needed to "pull" the gasses out - they will evacuate on their own provided the the breather tubes are not blocked. GD This is where you are wrong. Yes, the gasses will evacuate whatever overpressure of the blowby there is. But, you will never get any fresh air in. The crankcase will always be full of the acidic air. Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 As a custom trike, I doubt he has to pass any inspections. GD I missed the trike part. I dont understand CA emissions so I dont know how they handle things like that. Ive seen stuck or clogged pcv system blow seals, and pop out dip sticks. nipper Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 This is where you are wrong. Yes, the gasses will evacuate whatever overpressure of the blowby there is. But, you will never get any fresh air in. The crankcase will always be full of the acidic air. That makes no sense to me. If the crankcase "breathes" (and in a real sense it does - it pulls air in and out as the pistons pump) then it is exchangeing air through the valve covers. What action keeps it from exchanging the acidic portions of the crankcase air? "pressure" causes air to move. So "overpressure" is going to move the air around - and it's not a small amount of air either, so I just can't see a way for those gasses to build up with the constant pressure and airflow. GD Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 That makes no sense to me. If the crankcase "breathes" (and in a real sense it does - it pulls air in and out as the pistons pump) then it is exchangeing air through the valve covers. What action keeps it from exchanging the acidic portions of the crankcase air? "pressure" causes air to move. So "overpressure" is going to move the air around - and it's not a small amount of air either, so I just can't see a way for those gasses to build up with the constant pressure and airflow. GD as long as the engine is running you have constant pressure and airflow. This is where these gasses come from, the blow by from the rings which all engines have. nipper Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 as long as the engine is running you have constant pressure and airflow. This is where these gasses come from, the blow by from the rings which all engines have. nipper Yeah - that's how I understand it anyway. Plus when a sealed piston travels up in the cylinder, it displaces exhaust gases out of the cylinder (which is somewhat offset by other cylinders that are travleing downward in their bore's, but it creates airflow anyway), and at the same time it sucks fresh air into the crankcase from the breather tubes in the valve covers. Blow-by is only a small fraction of the composition of what's inside the crankcase - with open breather ports, it's mostly composed of fresh air. GD Link to comment Share on other sites More sharing options...
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