IceManRS305

iTrader: (-1)

i was wondering if it would hurt/help anything if i got rid of the PCV on my LO3 and threw some nice looking valve cover breathers on there and just plugged the PCV line to the throttle body... also i never can get a straight answer on this, what exactly does the PCV do... is it for emissions? or does it serve a bigger purpose and should just be left alone?

'86 350

I'd leave the PCV. It basically prevents sludge buildup down in the crank case and other places. It puts a nice vacuum seal on the rings too.

Leave it.

IceManRS305

iTrader: (-1)

dammit, lol..... than why do you see alot of cars with just breathers on the valve covers if its bad? im not argueing, just asking..... would i at least be able to get rid of the stock ugly breather filter on the passenger back vc?

bluegrassz

iTrader: (3)

I took mine off because of having room under the hood. I dont think a spacer under the carb will fit, but im going to try.

I ended up getting oil on top of my valvecovers from not having it hooked up.

si_camaro

The vapours floating around the crank case turn acidic after a time. You'll have to change your oil about once a week to keep up. It's not worth it, and you can get a nice looking chrome breather.

IceManRS305

iTrader: (-1)

ok sweet.... but im still curious why alot of ppl dont run PCV's if hurts the motor that bad?

Apeiron

Mostly ignorance, or they're racing and spend all their time at WOT anyway.

IceManRS305

iTrader: (-1)

huh.... good to know thanks alot for the help... my questions answered...

84z28350

Pop in a PCV, They do nothing but good. For a couple bucks you can get a fancy breather to put on the other valvecover, which has to be done for fresh air to enter the crankcase.

Sonix

iTrader: (1)

my chrome topped K&N one shows the red filter paper, *and* is chrome, nothing looks better than that.
Definately a good thing to have.

taonindo

i could be wrong but i think the pcv valve is a one way valve that helps clear unburnt gases from the crank case (where they could ignite) for a street car i wouldnt run with out one for very long.........tao

Randy82WS7

yes it pulls vapors out of the crankcase

the pop in breather filter thingies are used for the return

filtered return

into the crankcase


the pvc is where the vapors are pulled out\

you need it

leave it

68 was the first year for this closed system

in 67 and older all it was was a huge open vent in the rear of the block into the air

it has nothing to do with emissions, nor is it an emissions system



if you dont have it it will cause problems in your engine over time

the big ugly breather on the vc was originallpy not there and instead was a return tube connected to the air cleaner assembly and had a little filter in it, this si where the clean filtered air was returned into the crankcase to make up for the vaporous air being sucked out(and burned) of the crankcase in the driver side VC

Supervisor42

There is one major thing that most people miss about the PCV system. It provides the majority of air to the engine at idle. Almost all carburetors (except full race) are set up to count on this flow of air at idle.
What happens when the PCV is plugged off and this idle air is lost, is the carb idle circuit must be turned leaner. No big problem except the throttle plates must be opened to make up for the loss of air. You hear about people drilling holes in the throttle plates. If the carb is any good the main jets start to flow when the throttle is moved off of the idle position due to the increased air flow. What you wind up with is the idle circuit still flowing (because the plates are still closed) and the main jets dripping at idle due to the increased air flow. This will "wash out" the rings from the raw gas removing the oil at idle. Not to mention the vapors trapped in the crankcase condensing and forming sludge.
The humble PCV valve is more complicated than it seems also. It is not simply a check valve or an orfice that won't clog up. The valve is held almost closed at idle by engine vacuum since blowby is minimal. When the output of the engine increases the vacuum drops and the valve opens more to handle the increased blowby. Ain't that neat?
The reason you see multiple breathers on race-only engines is the thin rings (1/16") that they have to use for high rpm produce so much blowby that it overwhelms the PCV system. Watch tractor-pull setups and you will see 2 plumes of smoke coming from pipes at the bottom of the engine to handle this blowby.
End of PCV systems 101.