Is a PCV Valve Really Necessary?
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
I have always run a PCV valve on all my hot rods. I have one on the 406 in my signature. This engine was in my 80 Vette for a few thousand miles and the intake looks just as clean inside as when I put it on, just as clean as George's (Gkull), if not cleaner. The hose between the PCV valve and the vacuum port is clean and dry inside. If it is full of oil you have something wrong in the way the PVC is installed or the engine has excessive blow-by. I see no downside to running a PVC valve. There has not been an car produced since the 60's that did not vent the crankcase to the intake, even the 200 plus MPH supercars!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
Burning Brakes
Joined: Feb 2012
Posts: 925
Likes: 7
I currently have an electric vacuum pump for my brake booster. I will be replacing the vacuum booster with a hydroboost setup at some point. So, I've been toying around with the idea of adding an air/ oil separator maybe something like this http://www.jegs.com/i/JEGS+Performan...52206/10002/-1. Since I won't be using the vacuum pump for the brakes, I was thinking of connecting it to the air/ oil separator to kick in at WOT. Also keep the hose going back to the carb T'd into the vacuum pump line with a check valves so it will still function during normal driving. It will be a while before I'm ready for the hydroboost, so I'll probably just pick up the air/ oil separator for now. Any thoughts on the electric vacuum pump idea?
I'm no expert on this but I think WOT is a condition where there isn't enough vacuum to keep the PCV closed and there is high crank case pressure to be vented. So the pressure is bled off into the intake through the PCV valve. If during WOT, you apply the vacuum from the pump to the PCV, the valve will stay closed when it needs to open and the pressure will try to bled out through some other path, like the rear main seal or at the corners of the intake or pan or out the breather and on to the valve cover. You would need another check valve to keep the pump from pulling an air/fuel mixture out of the intake at WOT. Could get pretty interesting.
Last edited by Super6; Oct 8, 2013 at 09:14 PM. Reason: Added info.
Team Owner
Joined: Jul 1999
Posts: 65,492
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From: Orange Park Florida
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
I have always run a PCV valve on all my hot rods. I have one on the 406 in my signature. This engine was in my 80 Vette for a few thousand miles and the intake looks just as clean inside as when I put it on, just as clean as George's (Gkull), if not cleaner. The hose between the PCV valve and the vacuum port is clean and dry inside. If it is full of oil you have something wrong in the way the PVC is installed or the engine has excessive blow-by. I see no downside to running a PVC valve. There has not been an car produced since the 60's that did not vent the crankcase to the intake, even the 200 plus MPH supercars!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
The first two paragraphs here should tell you everything you need to know about why you should always run a pcv system.
http://en.wikipedia.org/wiki/Crankcase_ventilation_system
Burning Brakes
Joined: Feb 2012
Posts: 925
Likes: 7
I have always run a PCV valve on all my hot rods. I have one on the 406 in my signature. This engine was in my 80 Vette for a few thousand miles and the intake looks just as clean inside as when I put it on, just as clean as George's (Gkull), if not cleaner. The hose between the PCV valve and the vacuum port is clean and dry inside. If it is full of oil you have something wrong in the way the PVC is installed or the engine has excessive blow-by. I see no downside to running a PVC valve. There has not been an car produced since the 60's that did not vent the crankcase to the intake, even the 200 plus MPH supercars!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
I am not a greeny or tree hugger by any means, but I see no reason to pollute the air more than necessary. I too cannot stand the smell of crankcase fumes and they are detrimental to your health!
Burning Brakes
Joined: Oct 2011
Posts: 956
Likes: 86
From: McDonough Georgia
The PCV system is one of the only things to come out of the early smog cars that is worth using.
It is totally beneficial to your engine. It will clean and filter nasty crankcase gas and run fresh air through it.
Clean air is pulled through the PCV into the crankcase from the top of the air filter.
It should exit the other valve cover through a filter and via vacuum back into the base of the carb.
If you are using a filter, the nastiest gunk doesn't go back into your motor. And anyway, what is pulled in via the carb is reburnt.
A win win for the environment and your motor.
An open system doesn't use the vacuum of the carb to pull the fresh air through. It just vents to the engine compartment spraying a fine mist of gunk all over everthing. Also, since it isn't controlled by vacuum, a lot of crap stays in the engine.
Just putting vents in the valve covers equalizes pressure without any beneficial cleaning; other than what the spinning crank might pull into the motor.
It is totally beneficial to your engine. It will clean and filter nasty crankcase gas and run fresh air through it.
Clean air is pulled through the PCV into the crankcase from the top of the air filter.
It should exit the other valve cover through a filter and via vacuum back into the base of the carb.
If you are using a filter, the nastiest gunk doesn't go back into your motor. And anyway, what is pulled in via the carb is reburnt.
A win win for the environment and your motor.
An open system doesn't use the vacuum of the carb to pull the fresh air through. It just vents to the engine compartment spraying a fine mist of gunk all over everthing. Also, since it isn't controlled by vacuum, a lot of crap stays in the engine.
Just putting vents in the valve covers equalizes pressure without any beneficial cleaning; other than what the spinning crank might pull into the motor.
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Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
This ^^^...pre pcv era cars had road draft drain tubes that would drip oil out which was forced out by excess crankcase pressure.
The first two paragraphs here should tell you everything you need to know about why you should always run a pcv system.
Crankcase ventilation system - Wikipedia, the free encyclopedia
The first two paragraphs here should tell you everything you need to know about why you should always run a pcv system.
Crankcase ventilation system - Wikipedia, the free encyclopedia
Not all petrol engines have PCV valves. Engines not subject to emission controls, such as certain off-road engines
I've never noticed oil, or bad smells, I also run 192 - 195 stats and try and keep the heat up to make the engine more efficient. Higher operating temps also keep water out of the oil.
I think what it really comes down to is: does recirculating burnt gasses back through the intake increase HP or does fresh 100% outside air have higher HP?
As for me I need to spend some money on the Vette so I am installing a vacuum pump this winter and gaining HP
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
You didn't even read your own Wikipedia to the end.
Not all petrol engines have PCV valves. Engines not subject to emission controls, such as certain off-road engines
I've never noticed oil, or bad smells, I also run 192 - 195 stats and try and keep the heat up to make the engine more efficient. Higher operating temps also keep water out of the oil.
I think what it really comes down to is: does recirculating burnt gasses back through the intake increase HP or does fresh 100% outside air have higher HP?
As for me I need to spend some money on the Vette so I am installing a vacuum pump this winter and gaining HP
Not all petrol engines have PCV valves. Engines not subject to emission controls, such as certain off-road engines
I've never noticed oil, or bad smells, I also run 192 - 195 stats and try and keep the heat up to make the engine more efficient. Higher operating temps also keep water out of the oil.
I think what it really comes down to is: does recirculating burnt gasses back through the intake increase HP or does fresh 100% outside air have higher HP?
As for me I need to spend some money on the Vette so I am installing a vacuum pump this winter and gaining HP
Drifting
Joined: Apr 2002
Posts: 1,720
Likes: 19
From: Manhattan Beach Ca
Mine is a daily driver with two breathers. When rings didnt seat properly the breathers dripped oil. When new rings seated correctly breathers never dripped and stay white almost a year.
Never smelled any crankcase odors so not sure why people say that. Engine compartment is always clean, no mist. .02
Never smelled any crankcase odors so not sure why people say that. Engine compartment is always clean, no mist. .02
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
