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CC Advertisers
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08-27-2004, 07:20 PM
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CC Member
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Join Date: Aug 2003
Location: Toronto, Canada,
ON
Cobra Make, Engine: BRM #20, Ford 302, Holley 600dp
Posts: 93
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Not Ranked
Why am I running a PCV Valve????
Quick question...
If I'm not running emmissions, (exempt in Ontario)...then why am I running a pcv valve?...seems kind of redundant...
Thanks!
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08-27-2004, 07:38 PM
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CC Member
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Join Date: May 2004
Posts: 173
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Not Ranked
keeps the engine clean inside
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08-27-2004, 07:41 PM
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CC Member
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Join Date: Sep 2002
Location: Hickory,
NC
Cobra Make, Engine: ERA 427SC w/427so, ERA GT #2002
Posts: 1,106
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Not Ranked
The PCV valve is the best emissions device ever installed on an engine in terms of the good it does, i.e., suck all the bad stuff out of the crankcase. This bad stuff is blowby and water vapor. Blowby is made up of unburned combustion products and acid. You know what moisture does besides rust metal, it creates sludge. Be glad your engine is equipped with a PCV valve. 
__________________
Tom
"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough HORSEPOWER." Mark Donohue
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08-27-2004, 07:48 PM
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CC Member
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Join Date: Mar 2002
Location: Benton,
AR
Cobra Make, Engine:
Posts: 48
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Not Ranked
Just make sure it can get air in the other valve cover. (flow through ventilation) 
__________________
Age and knowledge don't always come together. Sometimes you just get the age...
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08-27-2004, 11:14 PM
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CC Member
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Join Date: Aug 2003
Location: Toronto, Canada,
ON
Cobra Make, Engine: BRM #20, Ford 302, Holley 600dp
Posts: 93
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Not Ranked
but it seems like whatever i'm filtering through the valve i'm just running right back into the carb am i not?
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08-28-2004, 04:38 AM
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CC Member
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Join Date: Aug 2004
Location: Jackson,
MN
Cobra Make, Engine: Ford, 390
Posts: 4
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Not Ranked
Yes that is true, the design of the system is that it gently sucks the vapors out of the crankcase and runs it through the cylinders to be sent out as exhaust. I personally have never been a fan, I built an engine for a friend and used 2 breathers (one on each cover) on it and he hasn't had problems. I built one for me with 4 breathers (2 each rocker cover), no problems after 28,000 miles.
Of course there are also vacuum pumps to create an internal vacuum in the crankcase that helps develop more power because of less blowby and allowing the engine to have looser tollerance rings.
__________________
Though, not perfect am I; my opinion is golden.
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08-28-2004, 07:00 AM
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Senior Club Cobra Member
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Join Date: Mar 2001
Location: Southern Connecticut,
CT
Cobra Make, Engine: SPF - 351W, 944 non-turbo
Posts: 2,105
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Not Ranked
It ventilates the crankcase. It should be vented to the base of the carburetor, not to a vacuum hook-up on the manifold!
Bob
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08-28-2004, 07:12 AM
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Member of the north
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Join Date: May 2003
Cobra Make, Engine: A Cobra
Posts: 11,207
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Not Ranked
Bob makes a very good point. The vac. hose should be connected to the base of the carb and the PCV valve. On the opposite valve cover there should be either a connection to the air cleaner or a breather.
The vac. hose removes every gas, mist and/or fart that forms inside the crank case and allows it to be burned. The breather/air filter connection makes sure the air being drawn from the crank case is not dirty, filthy sand impregnated junk. ( a little graphic, but this needed a bit of drama, LOL )
Just my $0.02
__________________
I'm a writer, feed the artist and buy a book.
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08-28-2004, 07:52 AM
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CC Member
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Join Date: May 2003
Location: Newburgh, IN,
IN
Cobra Make, Engine: 427SC Unique
Posts: 481
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Not Ranked
So you can suck crap out of the crank and let it cook on the valves and pistons and carbon everything up.
Double edge sword.
I have a breather on the back of the manifold and a K@N filter on each valvecover but no pcv valve. I change oil frequently and have it tested. Contamination is not an issue for me.
Good luck
Brent |
08-28-2004, 02:13 PM
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CC Member
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Join Date: Aug 2002
Location: Dacula, (Atlanta),
GA
Cobra Make, Engine: Unique 427 SC, Southern Automotive 427W Stroker
Posts: 1,649
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Not Ranked
I don't know how much the block pressure is reduced by the PCV system, but my last engine didn't have one and I went through rear main seals in about a week. This new one does have a valve and I haven't had a problem. I'm not sure the two are related, but it makes for a sensible rationalization.
__________________
After a good hard ride.....oil pressure is over 50, temp is below 190, she idles and no new dents. LIFE IS GOOD!
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08-28-2004, 02:29 PM
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CC Member
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Join Date: Jun 2001
Location: Washington DC Metro (Virginia),
VA
Cobra Make, Engine: Classic Roadsters, Tweaked 351W, T-5Z, CRII Tech Support Team.
Posts: 1,895
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Not Ranked
Not all polluion control devices are bad, or rob your engine of power. The PCV, or Posive Crankcase Ventilation is one of them.
The PCV valve fist started appearing in the early '60's to remove oil vapors fom the crankcase. Prior to the PCV, oil vapors were vented by a road draft tube which puffed the oil vapors into the air, and onto the road.
The valve operates on a spring which opens the valve only under vacuum, idling or cruise. When you open the throttle, vacuum is decreased and the valve closes under sping pressure. The PCV goes in one valve cover, and the breather (or connection to the air cleaner) in the opposite valve cover. You can put you hand over the beather opening and feel the vacuum. Without the PCV, you'd get oil all over your engine. The PCV, if kept clean with a little Gumout periodically, will last forever, and keep you engine innards clean. If it gets clogged, the extra air from the PCV is absent and the engine runs rich. |
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