Going thru things on my Skylark. Trying to tune the carb plugged in a vacuum gage to the back bottom port, quadrajet car, and j hac about 8 inches of vacuum and not much response from adjusting needles. With all vacuum lines hooked up I put a piece of paper over the oil breather cap and it was sucking the paper. Feared it was leaking intake, as I put the intake on late last year. Unplugged all vacuum lines and capped them off, then checked my vacuum gage, was at 13 inches of vacuum, and idled a lot better. Paper would not get sucked to the breather cap hole so I don't have an intake leak it looks like. Started hooking up lines and and got to my pcv and tharscwhdn my idle and vacuum went bad. Put my finger over hose that was hooked up to bottom of carb and bounded back to better idle and vacuum. It sounds like my pcv on back of intake has a vacuum leak. It has a new grommet and new pcv so not sure what or how to stop the vacuum leak. Unless I did the intake leak test wrong. Read The Wizards post on how to check and I'm sure I did it right. So how do I find/fix the vacuum leak at the pcv on back of intake?
PCV is basically a controlled vacuum leak on a normal basis. I think you have something else going on. Carbs can be deceiving with wrong gaskets, mismatched parts, etc. do you have a known good carb that you can use as a control?
I might have one around. The carb that's on it now was rebuilt by me with a carb expert walking me thru it right next to me. I can put my hand over the carb and it starts to stall. But I will swap out carbs and see where that gets me in the morning
You seem to have enough idle vacuum with that PCV hose blocked off to keep the ball in the valve closed at idle like it should be. New PCV valves have been known to be bad or have crap in them. Have you tried to flush out that valve from both ends? if the ball itself is misformed or pitted with some rust it will never seal at idle, likewise if the seat formed in the case of the valve is out of wack then a poor seal will result also. A simple test is to use your mouth to suck on the hose side with the valve straight up in the air, you should hear no air coming thru.
