Hy. After reading about the functionality and reasons for the PCV(positive cranckcase ventilation system)...system in our cars, at least in the 70's vehicles, and even in modern ones...(racing modern engines have the engine vented through breather filters/ bottles, etc, not into the intake manifold and air filter housing, unless racing requierements ask for compliance with manufacturers stock configurations.)... I learnt that the PCV system is meant to burn the oxigen depleted, hot and oily gummy like air, a by product of the moving of the engine parts within the engine block, and valve area, within the ignition chamber(cylinders), never to allow it to reach the atmosphere, for the purpose of air pollution, to burn it, and ,in a way, treat this air before the hidrocarbons and other materials go free into the atmosphere. There is no advantage for the performance of your motor in re/burning this air within the ignition chamber,{ carburetion, ignition within the chamber,intake manifold,all of this parts/situations requiere clean , cool air to go in, not hot, oxigen deprived,gummy mass of air which will take the place of clean cool air needed for combustion}it could only hinder performance and efficiency. This bad air raises the temp in the intake manifold, and the carburetor, aside from the gunk deposits it leaves inside carbs,air filters,intake manifold, etc.All vehicles have a hose comming from the rocker cover/valve cover into the carburetor air filter. The manifold is connected to the hose comming from the engine block through the PCV valve, which only opens under high to partial vaccumm(deceleration /idle and easy cruising). Some cars have no block hose, instead, a second valve cover/rocker cover opening/hose, this one to the PCV valve in the intake manifold. Under vaccumm, the pcv valve opens, and the gummy air by product of the engine work goes into the intake manifold, then into your pistons,certainly doing nothing good to the ignition/engine performance.This gummy air is displacing cool good air and mix from the carburetor, it is not just an add on, it takes space needed for the good air within the cylinder, more gunk, less space for good air. Well, at the same time, as air leaves the block through the pcv valve into the intake manifold, air is coming into the engine through the valve cover hose from the carburetor connection.This hose connection, within the same air filter housing shared by the carburetor barrels, is competing and robbing away air available for the carburetor, so, if not having a super charger, or cold air box to feed extra air into the air filter/carburetion, then, you can imaging the competition for air within the air filter housing.Even if you do,{have a extra available supply of air) still, you are not maximizing, you are loosing precious air flow.
When vaccumm drops, as in flooring ,pedal to metal, acceleration, fast moving, uphill, etc, the vaccumm in the manifold is not powerfull enough to open the PCV valve. Now, the ventilation avenue for the block is closed, and all the ventilation is done through the valve cover, out the valve cover hose, into your carburetor, all that gunk is being sent straight into the carburetor ,going into the cylinders, all mixed up with your gas and air, messing up the nice mixture we hope to send into the combustion/cylinder area for ignition and power development. Guess why some carbs look all gunked up. If a PCV valve is neglected, then all the time 100%, not only under acceleration(no vaccumm) the gunk comes out of the engine through the valve cover into the carb, making things much worse for the carb, for the ignition, for the power development. In any event, even if well taken care off, still, as described before, the damage is done.
By disconnecting the hoses to the carb and PCV valve, and connecting 2 breathers...(one for each hose)..., positioned at the same height as the highest one...(valve cover one is the highest, in case of the other ventilation avenue being the block vent.In case of 2 valve cover hoses, both would be at the same height)...for them to effectively scavenge the bad fumes from the engine,{pulling up effect, as in a smoke stack} and by taking away and closing the PCV valve opening...(pipe plug does it)...you will asure a clean carburetor, cool manifold, clean and efficient ignition within the cylider,excelent clean "meant to be" mixture through the carburetor,no vaccumm loss in the system...(used by the hoses of the PCV system, which could be used by your ignition distributor vaccumm advance, and by your carburetor.)...and a efficient, clean ventilation system(block) by which bad air, gunk, goes out of your motor, and only clean air goes in, not competing with the air available for the carburetor throttles, not re burning gunk. The mission of the ignition event...(Intake, compression, ignition,and exhaust )... is to produce power by pushing down the cylinder , creating power to move the crankshaft, and the reburning of bad air is not a requierement at all. With 2 breathers, the engine will take clean, fresh air in, and get rid off bad air out in no time, in an efficient manner, without any negative consecuences.
Enviromentally speaking, we are a minority, auto enthusiasts, and the impact on pollution is negliable, I am not advocating automakers to do away with the system of PCV, but in older cars, this system is not efficient. New cars are built with all this pollution devices into account, make up for the losses,there is compensation,{ 4 valves per cylinder,twin OHC, computer controled devices as oposed to vaccum control, more RPM, more torque,etc} well thought in the design process. Before, when many of our engines were designed,these devices where added on to engines already designed, never taken into account the cons of such intrusions into performance.
As said before, ventilation is needed, I never said get rid of the ventilation, the block needs to ventilate, my question and advice is, what are you doing with this gunk air, do you want to hinder your performance?.Why would you sabotage the perfect mix in your carburetor, the nice intake manifold, the temperature of your engine,it's performance, with gunk, hot oxigen dpleted bad air?
To finnish, a neglected PCV valve creates caos, that is the danger of using this PCV valve system. If it shuts close, then the engine will spurt gunk through the valve cover into your carburetor, and again into your engine,and worst, this valve cover is not enough to vent the engine,{only one avenue open } so, guess how is the gunk and bad air is going to come out,.... through your gaskets, that is right, causing a leaky engine, head, gas pump, oil pum, valve cover,rear seal,timming chain, etc gaskets will become avenues for hot pressurized air to exit the engine. Massive engine leakage, bad gaskets all around.It can become a costly proposition.
Hope to bring in some insight into the PCV system and its hindering on performance and efficiency.
Later.______________________________
