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.

 

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.

 

Thank you, 76supercab2, for your response. Here is a pic of my engine. You can see the pcv valve in the oil filler cap, and the hose from back of carb to valve cover on left.

 

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?

 

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?

 

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.

 

Thanks, Bear. BTW, amen to your signature.

 

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.

 

You should add:

"Why do I have to press "1" for English?"

 

ONE WORD...AMEN!!!!!!!

 

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.....

 

Que? No entiendo!!!

 

Actually you should run one and the reason why is crap will blow out onto you engine thru the breathers when you get to hotrodding around. Before the PCV system, engines had a "road draft tube" which was connected to the crankcase (ever seen and early FE, there is a big hole in the rear of the intake) and hung down under the car. The end was cut at an angle so as the car went down the road a suction was created and the vapers were sucked out of the engine and dumped on the road. Of course, the government couldn't allow this to continue so te PCV system was created to appease the enviormentalist.

 

Bear, so you are saying that if you run one of those caps like a K&N filter one (like the racers use) it will blow stuff on your motor?

 

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.