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I just tuned up my 67 six cyl, new plugs,wires,cap,roter.pcv valve and hose, electronic points,oil & filter, fuel filter. I runs much better in park and in drive, but I still have a very slight rough idle. The new pcv took out 95% of the rough idle. When I remove the pcv valve and plug the botton with my finger or pinch the hose while in park it smooths out and purrs like it should. The vacume is sucking up the pcv valve and I pushed up on the inside of the valve and there was no change. Can I plug the vacume at the carb or will that cause a porblem? Any suggustions. Thx [&:]
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Change the PCV valve. Your description is exactly what you would expect from a bad PCV valve. You don't want to run without a PCV valve because it prevents moisture buildup, and redirects blowby gasses back into the carbwhich can lead to sludging of the oil. Anyway, they are pretty cheap.
Obviously, aPCV valve is a controlled vacumn leak. So covering it up makes sense to smooth out the idle. However, you still have the idle fuel calibrated to a controlled leak and the engine shakes. This means it's too slow or its too lean. Try to richen up the idle with the carb fuel screw. you could also try another PCV valve in the case that the one you have is a little too much leak and make sureyouhave the idle speed set correct and timing set correctly.
Did you try adjusting the idle mixture?
I'm not familiar with your carburetor, but I think they are all pretty much the same. With the car off but warmed up, screw the needle valve in until it lightly seats (remembering how many turns in just in case it won't start) then back it out 1/2 to 1 turn. Start the car, slowly turn valve in (cw) until the engine starts to run rough, then slowly turn it out (ccw) until it stumbles, then back in until it smooths out, looking for smoothest operation. If you have a vacuum gauge you should adjust it for the highest vacuum reading. Make sure the choke is open.
As with just about everything, I have had defective brand new PCV valves. Have you hooked a vacuum gauge up to see what you are pulling. If you have a realy lopey cam, you may not have enough vacuum for the PCV to function properly. Also like the previous posts, the carb need to be set properly.
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