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Old 01-20-2010, 04:43 AM
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PCV Valve

Is it possible to eliminate or bypass the PCV valve?
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Old 01-20-2010, 05:28 AM
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Ayuh,... I suppose you could just convert it to a road draft tube,...
But,...
That brings up the question,..... Why,..??
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Old 01-20-2010, 05:29 AM
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It is possible to eliminate it, but a evacuation system of some sort is needed.
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Old 01-20-2010, 06:54 PM
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I gotta go with Bondo... "why?"
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Old 01-20-2010, 11:51 PM
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that brings me to ask the same thing... why???? the whole point of the pvc valve is to relieve crank case pressure... witch is caused by a small amount of blow by from the rings... so all you really half to do is make sure its not sealed. because if the motor is sealed it will push the oil out all around the oil pan to release the crank case pressure... had it happen, thats how i learned... lol i was young... any way i have just used the push in breathers before and not had a problem, the only down fall is once the breathers get dirty they get your valve covers dirty... just wipe them off and go buy some new breathers... no big deal... the pvc valve sucks the crank case pressure out... but if you just use the breathers the pressure just vents through the breathers... so all i really half to say is just make sure you dont just seal the motor up, make sure it can relieve that crank case pressure somehow...
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Old 01-21-2010, 04:32 AM
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pcv

The reason I was interested in eliminating it is because my balancer shaft oil seal popped out of it's recess. Possibly because of excess pressure in the crankcase. However like you said it should be in working order to effectively do the job.
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Old 01-21-2010, 06:10 AM
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Without a properly working PCV system or some other type of evacuation there will be more pressure inside the engine. I have never tried to measure it but there would be a slight vacuum inside the engine with a evac system working properly.
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Old 01-21-2010, 08:59 AM
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not only that.. but w/o PCV you will have a lot of sludge and other build-up problems inside the crank case.. including having to more frequently change your oil.

if you are blowing seals out.. you might start with a leak down test and make sure you haven't got a cylinder with serious blow-by issues...

i had a worn out chevy 350 that would blow the oil dipstick out of the tube everytime I got on it cuz of the blow by
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Old 01-21-2010, 11:57 AM
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Quote:
Originally Posted by bergie
The reason I was interested in eliminating it is because my balancer shaft oil seal popped out of it's recess. Possibly because of excess pressure in the crankcase. However like you said it should be in working order to effectively do the job.
Removing the PCV valve would only make that worse...
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Old 01-22-2010, 09:57 PM
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I checked the operation of mine because I've developed a rear main leak. From what I could find on the net, it's supposed to pull 1-3 inches of guage vacuum. It had zero and I'm not sure if the spring is too weak (it's a couple years old). I have 18" manifold vacuum and very very little was getting past the valve...at least not enough to pull vacuum and help prevent oil leaks at idle. I'd like it to pull a little vacuum at idle but I'm not aware of "custom" pcv to allow this.


As far as the leak, also, I changed oil brand from Mobil 1 5w-30 to Motorcraft 5w-30 and also went from a 160* thermostat to a stock 192* to have some heat here in NC after moving here from Houston. I'm thinking switch everything back. Maybe the rear main cap will not expand as much and keep the seal tighter against the crank.
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Old 01-22-2010, 11:27 PM
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the PCV valve isn't there to relieve pressure from the crankcase.
the hose to the crankcase filter does that job.
the PCV valves' job is to remove the harmful vapors from the crankcase and only does that at idle and light throttle.
when your on the gas more than about 1/4 throttle, there little to no intake vacuum, but there is more blowby at that time.

also, don't run 2 PCV valves, it does no good to do so and it will cause oil leaks if you don't have a crankcase breather on the motor.
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Old 01-23-2010, 10:08 AM
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If you do a search on here you can find all the info you are looking for or most of it anyway. Click the link and search through it maybe it will help. http://www.hotrodders.com/forum/sear...archid=3287958 .


Cole
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Old 01-23-2010, 12:57 PM
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Quote:
Originally Posted by Soul_Hunter
the PCV valve isn't there to relieve pressure from the crankcase.
the hose to the crankcase filter does that job.
the PCV valves' job is to remove the harmful vapors from the crankcase and only does that at idle and light throttle.
when your on the gas more than about 1/4 throttle, there little to no intake vacuum, but there is more blowby at that time.

also, don't run 2 PCV valves, it does no good to do so and it will cause oil leaks if you don't have a crankcase breather on the motor.
/The pcv valve IS there to Ventilate POSITIVE CRANKCASE PRESSURE. The opposite valve cover provides fresh filtered air to the crankcase. Yes, it does remove aerated oil and unburned fuel/ combustion by products that get past the rings. At idle the pcv is practically closed. Only enough air gets by to make a hissing sound and this is correct operation. When there is little to no vacuum the spring pushes the valve down letting more blow by pressure to be released from the crankcase.

This is how internet misinformation comes about. If you disagree go read some fsm's or aa1car.com. They have a lot of information. That or just understand pressure differential.
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Old 01-23-2010, 05:44 PM
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ok so that brings me to ask is their a reason to cant just run two breathers one on each valve cover?
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Old 01-23-2010, 06:25 PM
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The PCV system does a lot of good. It sucks unburnt gas vapors out of the engine, and helps keep water condensation out of your oil. The gas vapors returned into the intake manifold make it possible to run a slightly leaner mixture, or if you have a car with O2 sensors on it, the cars computer does it automatically. In most cases, the crankcase on a PCV system operates at a slight vacuum, and this really helps to reduce any oil leaks in the engine.

If you just dump the blowby gasses into the air, through a breather system, you are wasting the gasses, and they really do add a lot to smog, far much more than if the blowby gasses were routed back into the intake, and burned.

For what it is worth, I am working on a 1947 Willys jeep, and it has a PCV system on it.

As far as different emissions systems go, the PVC system is good. It does not rob power. It helps your engine last longer, and stay cleaner. It reduces your cost to run the engine, and helps you get better mileage.

You will be better off leaving the PCV system intact on your engine.
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