What is a pcv and why do i need it

[wesleydax]

Just changed back to a carb from efi. everything changed out and running good. cranks when hot or cold. and getting about 11mpg. i noticed tonight while checking the fluids i had not changed the 5.0 valve covers. I have my old M/T covers i can use. do i need to? If so why. Ive heard and replaced many pcv but have no clue as to there use.

 

[Viperwolf1]

http://classicbroncos.com/forums/showthread.php?t=197866

 

[ObscureMachine]

It does this

 

[wesleydax]

well crap now i got to go change covers before we leave for mountains in the morning. Thanks guy good info

 

[wesleydax]

another question would it hurt to run it about 60 miles before changing them? what could i hurt

 

[patterdale]

The pvc valve was meant to open with the vacuum of the engine and suck any blowby gasses into the intake to burn up. It was the first form of pollution control device known to these little babies. They were good for that but were meant to close if the valve cover pressure exceeded the pull of the intake vacuum. A lot of them didn't close and resulted in oil in the air cleaner. You will need it to pass emisions tests in your state if original equipment is required to title/register your bronco.

 

[wesleydax]

ok just changed the valve covers back to the old ones. is it me or does the eng run easier.

 

[shamu]

Here is a no PCV Mexico Block 302 with 4 IDF44 Webbers. Note there is a 12 volt vacuum pump with a resivoir for the power brakes.
It is a expensive way to stay naturally asperiated.

 

[broncnaz]

Basically the engine or should I say carb is more or less tuned to run with a PCV in place years ago before PCV a lot of engines just had a open tube that allowed blowby gases to just vent to the ground.
Biggest issue with running no PCV is you still need to vent the gases or you will blow seals out of the engine.

 

[red hot71]

A engine needs crankcase ventilation. With the piston moving up and down they cause positive presure inside the crankcase, without it oil can be pushed past the seals or seals can be blown out.

If you look at the picture filtered air is supplied to the engine on the the drivers side valve cover and a pvc valve on the passenger side returns it to the engine thur vacume.