PCV Valve
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PCV Valve
The 390 (originally 360) in my 73 F100 auto 2wd has a PCV valve in the oil filler cap but there is no vacuum hose attached to it. The vacuum hose from the back of the carb goes to the other valve cover. The truck runs ok, but not great. Should I do something about this (and if so, what?) or should it be ok as is?
Thanks.
Thanks.
Postmaster
Joined: Feb 2003
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Do you have a picture of this?
The PCV valve should be on the hose connected to the vacuum meter the crankcase vapor to the intake.
The PCV system on my 390 is
PCV valve in passenger valve cover next to firewall
Hose from valve to back base of carb
Oil fill cap on driver side valve cover with hose to air filter mounted in air cleaner assebly.
Putting the valve on the intake side of the system will not allow the system to function properly.
The PCV valve should be on the hose connected to the vacuum meter the crankcase vapor to the intake.
The PCV system on my 390 is
PCV valve in passenger valve cover next to firewall
Hose from valve to back base of carb
Oil fill cap on driver side valve cover with hose to air filter mounted in air cleaner assebly.
Putting the valve on the intake side of the system will not allow the system to function properly.
Post Fiend
Joined: Mar 2004
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From: Union, Washington
The valve on the drivers side is doing nothing. The active PCV valve is on the passengers side in the groument in the valve cover and is going to in underside of the carb for a manifold vacuum to pull the nasty stuff out of the crankcase. The side with the breather with the valve sticking out the top of it is the air inlet to the crankcase and there should be a hose going to the air cleaner and a small filter on the inside of the air cleaner. Are you sure it is a valve or just an elbow?
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OK, I'm not smart but I'm pretty 
There is a pcv valve on the passenger side with a vacuum hose going to the back of the carb, I just pulled it out and looked at it for the first time. There is also an identical pcv valve in the oil filler cap. There is currently no hose attached to this one. Does this create a vacuum leak or other probs? Should I get a hose to run to small filter in the air cleaner?
There is a pcv valve on the passenger side with a vacuum hose going to the back of the carb, I just pulled it out and looked at it for the first time. There is also an identical pcv valve in the oil filler cap. There is currently no hose attached to this one. Does this create a vacuum leak or other probs? Should I get a hose to run to small filter in the air cleaner?
Last edited by rhenderson1965; Oct 26, 2006 at 07:44 PM. Reason: misspelling
Post Fiend
Joined: Mar 2004
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From: Union, Washington
It will let dirt into the crankcase of you motor, not a good thing. With the motor idling, plug the hole in the middle of the breather. If the rpms don't change then just plug it and forget it. If they do, you need to either clean the breather and see if that changes anything or get a different breather without a hole or run the hose to the air cleaner like a stock setup.
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Post Fiend
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From: Union, Washington
Originally Posted by rhenderson1965
Thanks, Bear. BTW, amen to your signature.
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From: Centreville USA
Originally Posted by Bear 45/70
Interesting that you mention my signature. I got reamed on another forum today for it and the position it takes. Seems I'm Not PC. What!, man I didn't know that.
"Why do I have to press "1" for English?"
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A PCV valve isn't required if you don't want to run one. The only thing you do have to do is make sure you either have a pcv valve or one of those breather type caps in your valve covers. All it is there for is to let the crankcase breathe or release built up pressure. I have heard of people pluging both valve covers without some sort of vent for the crankcase and it would either blow the dipstick tube out or push oil out the first easy hole it can find. JMO.....
Post Fiend
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From: Union, Washington
Originally Posted by pbear6969
A PCV valve isn't required if you don't want to run one. The only thing you do have to do is make sure you either have a pcv valve or one of those breather type caps in your valve covers. All it is there for is to let the crankcase breathe or release built up pressure. I have heard of people pluging both valve covers without some sort of vent for the crankcase and it would either blow the dipstick tube out or push oil out the first easy hole it can find. JMO.....
Postmaster
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I think he means if you run breathers on both valve covers. A breather cap on the driver's side with the pcv hooked up on the passenger side is functionally equivalent to the stock setup. The stock cap connects to an air filter in the air cleaner housing. I see no difference in having the air filter as part of the cap.
However, if you have serious blow-by, then yes you could get crap on the motor I guess. But if that's the case, then you'd proabably also get oil and crap in the air cleaner housing too.
However, if you have serious blow-by, then yes you could get crap on the motor I guess. But if that's the case, then you'd proabably also get oil and crap in the air cleaner housing too.