2 Breathers and No PCV???
Thread Starter
Instructor
Joined: Mar 2003
Posts: 235
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2 Breathers and No PCV???
Does anyone know what the benifit if any is to using 2 breather elements in the valve covers with no PCV. I have seen it mainly on hi performance engines and I am curious as to its purpose. What do you gain by eliminating the PCV valve? Just wondering if anyone knows that can enlighten me. thanks.
Team Owner
Joined: Jul 2001
Posts: 182,997
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From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Re: 2 Breathers and No PCV??? (IRON WILL)
I used to run 2 Breathers.. Now I'm running 1 Breather and 1 PCV Valve.. Didn't notice any difference between both setups...
Le Mans Master
Joined: Nov 1999
Posts: 5,768
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From: San Diego CA
Re: 2 Breathers and No PCV??? (IRON WILL)
What do you gain by eliminating the PCV valve?
Since the PCV is designed to ventilate the crankcase and if the crankcase is not adequately ventilated, the motor oil will quickly become contaminated and heavy sludge accumulations will begin to form. Internal parts, not protected by the motor oil, will begin to rust and/or corrode due to the water and acids that will become trapped within the crankcase.
you see it on "high performance" engines probably because the owners of the engines see it on race cars and think - oh-ho this is a performance add-on. Real race engines dont want to pollute the a/f mixture with bypass gasses and since the engines are rebuilt after every use - any possible effect is eliminated - in fact they evacuate their crankcases with either a vacuum pump or by having header attachments that suck the blowby gasses out and burn them in the header collector.
[Modified by fauxrs, 1:30 PM 6/12/2003]
Race Director
Joined: Mar 2001
Posts: 11,322
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From: Living in the Hartland
Re: 2 Breathers and No PCV??? (IRON WILL)
Another not to run it with two breathers is oil can blow out the breathers and get all over the eng compartment. With the pcv it sucks in air through the breather on the opposite side of the eng. Another reason is the smell. :U
Race Director
Joined: Mar 2001
Posts: 11,322
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From: Living in the Hartland
Re: 2 Breathers and No PCV??? (bluevetteman)
Heat rises so the hot oil fumes will naturally want to rise out into the eng compartment when it is cooler than the eng or be pulled out when the car is moving and there is a pressure diff between the eng and the surrounding air. Roll your window down at 80 mph and blow smoke at the crack to see what I mean.
Safety Car
Joined: Jun 2001
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From: Severna Park Md
Re: 2 Breathers and No PCV??? (Fevre)
The only advantage i know of not running pcv is if you have a really big cam that has low vacuum in the lower rpm range. By plugging the pcv it helps restore some of the lost vacuum. I once had a 455 olds with a really radical cam. It idled and ran better down low without the pcv. But it did stink like heck though.
I pretty much agree with all the statements above as to the dis-advantages of not running pcv.
I pretty much agree with all the statements above as to the dis-advantages of not running pcv.
Team Owner
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
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St. Jude Donor '06-'10, '13
Re: 2 Breathers and No PCV??? (Jvette73)
The only advantage i know of not running pcv is if you have a really big cam that has low vacuum in the lower rpm range. By plugging the pcv it helps restore some of the lost vacuum. I once had a 455 olds with a really radical cam. It idled and ran better down low without the pcv. But it did stink like heck though.
I pretty much agree with all the statements above as to the dis-advantages of not running pcv.
I pretty much agree with all the statements above as to the dis-advantages of not running pcv.
We have a winner.
The non-pvc system is mostly used on hi-performance engines that don't see any real mileage. The big cams cause the PCV to not work at all as there is not enough vacuum to overcome the spring in the PCV valve at idle. The only time the PCV would work is when decelerating.
That is why some hi-po motors use a PCV system that uses the exhaust to scavange the crankcase fumes instead of using the carb. The exhaust system has enough flow to do positive ventilation and this will help the rings seat (less blow-by) and less oil leakage around gaskets and seals.
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