PCV valve Necessary ?
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Senior User
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PCV valve Necessary ?
I notice that when I took off my pcv valve and places my finger over the hole my truck idled better than normal(it normally misfires) is the pcv valve a item that needs to be on my truck or can I plug the holes and run it that way? It goes into the valve cover and then into a spacer in my carb
i got a new valve and new hose today and it runs the same
Necessary or would it be better to plug the holes?
i got a new valve and new hose today and it runs the same
Necessary or would it be better to plug the holes?
Posting Guru
Joined: Aug 2002
Posts: 1,214
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From: Minneapolis, MN
PCV valve Necessary ?
You're much better off running the PCV valve. Even though it is a metered vacuum leak and the idle mixture has to be adjusted to compensate (hint, hint) 
the PCV valve keeps the blowby in the crankcase from contaminating the oil. It also slightly reduces the pressure in the crankcase so you have fewer leaks, etc.
You just need to adjust the idle mixture on the carb for the best idle. Have you checked for any other vacuum leaks?
the PCV valve keeps the blowby in the crankcase from contaminating the oil. It also slightly reduces the pressure in the crankcase so you have fewer leaks, etc.You just need to adjust the idle mixture on the carb for the best idle. Have you checked for any other vacuum leaks?
Posting Guru
Joined: Feb 2002
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From: Atlanta, Georgia, USA
PCV valve Necessary ?
A PCV valve is not just an emissions thing, it actually helps you engine live longer for the reasons that macguyver mentioned. When your engine is running, some gasses "blow by" the pistons, and get into your crankcase, which will let gasoline in your oil, which breaks it down into sludge. A PCV valve keeps a vacuum going inside the engine, so any gasses that get by get sucked into the engine and burned again before they contaminate the prescious parts inside your engine. I also agree with macguyver in that your carb is most likely not perfectly tuned, or may have a vacuum leak if it runs better when you plug the hole. I prefer to run the PCV into the carburetor, if your carb has an outlet for it, that way you get a more consistent mixture. What kind of carburetor do you have? You should also make sure that your PCV is clean, if not, you can replace it (~$1.99) or just clean it with brake parts cleaner.
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PCV valve Necessary ?
Yea it’s a rebuilt Holley carb 2b and i have replaced everything and checked for leaks else ware
Im going to adjust the mixture and see if I can get it to smooth out a bit
I know I don’t know too much of what im talking about (so thanks for your patience) but in the other valve cover there is another hose that went to my stock air filter it seems to be the same as the other one but on the back of the covor, should it have a pcv valve too? Or is the hose just good how it is?
Thakns again for your help i am learning a lot on this forum
Im going to adjust the mixture and see if I can get it to smooth out a bit
I know I don’t know too much of what im talking about (so thanks for your patience) but in the other valve cover there is another hose that went to my stock air filter it seems to be the same as the other one but on the back of the covor, should it have a pcv valve too? Or is the hose just good how it is?
Thakns again for your help i am learning a lot on this forum
Posting Guru
Joined: Feb 2002
Posts: 1,712
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From: Atlanta, Georgia, USA
PCV valve Necessary ?
The other hose that goes to the air cleaner is where the PCV gets fresh air from. In other words, air flows through your engine the whole time its running, it comes in the hose the comes from your air filter, and gets sucked back out the other side by the PCV valve, then into the carburetor where its burned. If you ever do away with your stock airlid, make sure you replace that filler hole with a filtered breather, otherwise the PCV will suck infiltered air into your engine. It's good to hear you're running better now.
