WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 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 Refresher on how a 4 cyl. boxer engine operates. For every piston moving up, there is another piston moving down at an equal but opposite rate. This is what makes them balanced. So, you will get flow forward and backward in the block, but the only flow out of the block will be blowby, and there will be no flow in. The pistons moving upward are cancled by the pistons moving downward, hence no pumping action. Blow by is the majority of whats in the crankcase. As a test: cap of the hose hookup on the block. Leave the two cam covers open. Rev the engine up to 3k rpms (or higher if you don't have neighbors) now put your fingers near the valve cover ports. You will have blowby whooshing out, and nothing getting sucked in. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 I see what you are saying. The valve would provide some exra flow for fresh air into the passenger side valve cover, but it would have to be hooked up to the valve covers such that one is attached to the PCV, and the other sucks clean air for it to work. Most hot-rods aren't setup that way, and the use of valve cover breather filters is pretty commonplace. I don't see it as being a huge issue. You don't see crankcase explosions from bad PCV valves. They just cause blown seals generally. The pumping action of the pistons creates a swirling action of the air in the crankcase, and it's going to do some fresh air exchange - the PCV would help it to do more, but I don't see it as being horribly detrimental to not have it. GD Link to comment Share on other sites More sharing options...
WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 You wanted research? Here's research: Pg. 540: "Gasoline vapor and steam are harmful if they are allowed to remain in the engine oil. Steam will condense and mix with the oil to form a sludge, while gasoline vapor will condense and dilute the oil. Two different methods are used to remove these vapors from the crankcase. The first method consists of a breather tube wich depends on the flow of air past its open end to remove the vapors. The second method, known as positive crankcase ventilation, utilizes the intake manifold pressure to circulate air through the crankcase, returning the vapors to the combustion chamber for removal." Bricker, Frederick E. "Automobile Guide." 1966. Theodore Audel & Co. Indianapolis Indiana Pg. 17-11: "It is vitally important that crankcase fumes be drawn off by the crankcase ventilation system. A ventilating system working poorly or not at all will permit a rapid buildup of sludge, water, acids, ect., that will shorten the service life of the engine." Pg. 17-14: "Remember the PCV system MUST be kept CLEAN. Rough idle, poor mileage and rapid engine wear will result when the system is inoperative." Stockel, Martin W. "Auto Service and Repair." 1969. The Goodheart-Willcox Co., Inc. Homewood, Ill. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 28, 2006 Share Posted December 28, 2006 Cool - well I guess I need to hook mine up, or drop a tube down under the car. Good thing I change my oil regular like. Thanks for the references - good info. GD Link to comment Share on other sites More sharing options...
WoodsWagon Posted December 28, 2006 Share Posted December 28, 2006 As for the hotrods not having a PCV system, This is from a flathead ford v8 forum: "Standing on my "soapbox" for a second; Flatheads are NO different than new engines, there WILL be some blow by, AND condensation does form in the crankcase, so using some form of PCV (positive crankcase ventilation) WILL make your flathead live LONGER!! The "trick" is to use a system no one can spot easily!!" Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 As for the hotrods not having a PCV system, This is from a flathead ford v8 forum:"Standing on my "soapbox" for a second; Flatheads are NO different than new engines, there WILL be some blow by, AND condensation does form in the crankcase, so using some form of PCV (positive crankcase ventilation) WILL make your flathead live LONGER!! The "trick" is to use a system no one can spot easily!!" Some just use the simple breather tube, since some engines get rebuilt after race day. nipper Link to comment Share on other sites More sharing options...
trikerbob Posted December 28, 2006 Author Share Posted December 28, 2006 Well of course I'm throughly confussed now. Some say no big deal, others say big deal. I'm inclinded to go with the no big deal crowd. My reason has to do with all the motors I've used in the past that had nothing but just one little crank case breather hose on them with no valves that opened or closed and they seemed to do just fine. I've been dealing with VW motors for several years in my Trikes and they all only have one little breather hose on them and no PCV or anything else. So I guess I'll just have to try it this way for awhile and see what if anything happens. I'm inclined to believe that the PCV along with the overwhelming amount of vacumm lines and little do dads that I pulled off this motor, is total bull crap. I thank you all for your input non the less and I'll watch the motor real close and see if anything seems to be happening. If I notice anything strange going on, it will be easy enough to hook it up. But I doubt that I'll ever feel the need. Bob:burnout: Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 so 50 years of engineering that has proven itself is wrong.... very well, then have fun with the trike. nipper Link to comment Share on other sites More sharing options...
keltik Posted December 28, 2006 Share Posted December 28, 2006 so 50 years of engineering that has proven itself is wrong.... Personally i would hook it up. I realise and appreciate having a clean engine is nice, but a PCV system is only 3 extra hoses, why not fab up some stainless ones and make it look flashy. I think when these PCV systems were designed they had a car environment in mind where it HAS to last a good few miles. But i think on a weekend trike it wouldnt make too much of a difference. Oh yeah and btw the other purpose of the PCV valve is to give us something to *************** about and to give the dealers another way of pulling cash from our pockets. Link to comment Share on other sites More sharing options...
jacobs Posted December 28, 2006 Share Posted December 28, 2006 The earliest I recall seeing a PCV was on a military Jeep either WW2 or Korean Conflict vintage. It was used to help keep water out of the engine when fording rivers. Link to comment Share on other sites More sharing options...
trikerbob Posted December 28, 2006 Author Share Posted December 28, 2006 Well this was all very interesting. You all seem to have a very convincing argument to hook it up. So I might just go ahead and do it. Either way, I don't think its that big a deal but if over the long haul it helps keep the motor in better shape, its worth it. By the way, Trikes here in Calif or at this time all states do not require Trikes to be smoged or checked. However that day is coming in the not so distant future. But for now, My Trike does not need anything smog related on it, so its all been removed and all the little vacumm holes pluged. My Trike is my daily driver in all except very bad weather. Its not a weekend thing as it is with some. I average around 7 to 10,000 miles a year on them. Thats my main reason for building this one with what I hope to be a better motor than the VW motors I have been running. I'm tired of all the constant tinkering that must be done to the VW to keep them running good. I'm expecting better fuel economy, better horsepower, and wider power band from the Subie, and above all else, not as much tinkering to keep it alive. Thanks for all your input. Bob Link to comment Share on other sites More sharing options...
keltik Posted December 28, 2006 Share Posted December 28, 2006 I'd be interested to know if your keeping the timing belt covers on or not? Link to comment Share on other sites More sharing options...
nipper Posted December 28, 2006 Share Posted December 28, 2006 Catalysist are coming soon on all engined, including outboards, conversions and motorcycles. Oddly computers have made this easier. Going to be interesting to see how theyfit cats on small engines and how they actually enforce the regulations. nipper Link to comment Share on other sites More sharing options...
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