PCV valve:

[vandelay industries]

i know how the pcv system works, but how does the actual pcv valve work?

i ask because out of curiosity i sucked on it like a straw because i thought at high vacuum, it's not supposed to let a whole lot of air in----yet mine did.

 

[JoshHefnerX]

It's a 1 way valve - check valve, that's what that rattle inside is.

 

[vandelay industries]

Right, but i sucked on the end that goes towards the carb or manifold and it let in as much air as i could breath in. i did this because i'm trying to figure out how the engine can idle with all that air coming in----if, in fact it supposed to be letting all that air in? Right now, my pcv is disconnected because i was trying to get various carbs idling right and now i want to re-connect it.

 

[JoshHefnerX]

That's how they're supposed to work. Blowby gasses are supposed to be allowed from the crankcase into the manifold, but not the other direction. It should block air if you were to have blown out that direction.

 

[diesel4me]

The older carbed engines were designed with air-fuel mixtures that allowed for the "vacuum leak" the PCV valve allowed...not sure how EFI engines adjust for it,probably controlled by the various sensors and the ECM..

I tried blocking off a PCV valve once on a 283 I had that had a lot of blowby ..doing so made it much worse,and fouled the spark plugs rather quickly,they sooted up with fluffy carbon like I had forgot to open the choke and drove it 100 miles..the vacuum "leak" allowed by the PCV valve made all the difference,without one it ran way too rich....