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Noob
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Discussion Starter #1
Ok so I've seen a bunch of threads on breathers, but none explain what the purpose of them are? Or really how to even install them and I'm just really curious about it.
 

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FBGM
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6,177 Posts
Boss should come in since he runs them, but what they do is vent the crankcase pressure, all you do is cap the intake and then put breathers on both nipples on the valve covers, literally a 5 min job.
 

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Eat Springs, **** Valves
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They vent crank gases to the atmosphere instead of recirculating them into the engine. They made my interior smell like oil, so I stopped running them.
 

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Noob
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Discussion Starter #4
So it just eliminates nasty oily air from going back into the engine? What happens with the breathers then? Wouldn't it just leak? I want to run them cuz I'm trying to make the engine bay look nice and clean and get rid of hoses, but that sounds like it might make it worse.
 

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Bob The Mo'fukkin Builda!
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i think i'm the only person i know of that has had problems running them. when i installed them my car throws fault codes and also gets a wrench light. pulled them off and put the stock stuff back on and i have no issues. i've been meaning to buy a catch can, but haven't yet
 

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Registered
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breathers are very important
i tried to put an oil cap on my car for only 1 hour and there was so much crank case pressure that my whole dip stick flew off the block!!!!! that **** is serious
just get after market valve cover and get them with whole and go get 1 or 3 k&n breathers and your car will run 10 X better
its very important for force induction as well
 

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Eat Springs, **** Valves
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9,332 Posts
breathers are very important
i tried to put an oil cap on my car for only 1 hour and there was so much crank case pressure that my whole dip stick flew off the block!!!!! that **** is serious
just get after market valve cover and get them with whole and go get 1 or 3 k&n breathers and your car will run 10 X better
its very important for force induction as well
lolwut.
 

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Bob The Mo'fukkin Builda!
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10,234 Posts
breathers are very important
i tried to put an oil cap on my car for only 1 hour and there was so much crank case pressure that my whole dip stick flew off the block!!!!! that **** is serious
just get after market valve cover and get them with whole and go get 1 or 3 k&n breathers and your car will run 10 X better
its very important for force induction as well
we aren't talking about a fox body. no need to buy new valve covers for hundreds of dollars. also maybe you should have thought about a pcv valve to keep the pressure from blowing your dipstick out.
 

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we aren't talking about a fox body. no need to buy new valve covers for hundreds of dollars. also maybe you should have thought about a pcv valve to keep the pressure from blowing your dipstick out.
just telling him my experience and how it helped my car run better
 

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If you were NA or supercharged under 450rwhp, I'd say an oil separator would control blow-by and do it well, but over 450rwhp the breathers on both sides (as suggested by DeadlyVenon97) is the way I would go. In any case, either run the system “sealed” with a quality oil separator on the driver side, or open the system with breathers on both sides. The best explanation I've read was from Jim Sr. of JDM Engineering on another forum. Here's a quote:

Originally Posted by JDM's owner
There is no right or wrong with oil separators. We just choose not to use them because to make it work properly you have to have a sealed system. What I mean by sealed system is no breather caps or any other evacuation device hooked to the engine. Some of the oil buildup in the supercharged cars is from reversion on decel. These motors are extremely tight and on hard decel you can pull 30 inches of vacuum, which will allow oil to be sucked back through the guides. With a sealed system that will still occur. With an oil breather cap, that will not occur. If a car is running enough power, say 500whp+, we will stick a breather cap on it. This helps two things. 1 is to control the oil being sucked through the guides on a hard decel and 2 pressure or boost that seeps past the rings will get blown out the breather cap. Once oil goes past the guides, it actually goes back up through the intake tract and gets sucked up into the supercharger. On a sealed system, under hard accel, as soon as you shut the throttle body, the motor is going to do everything it can to pull air from somewhere. The path of least resistance is the crankcase - it will pull it past the rings, from the PCV system, and even from the rear main seal - with the breather cap you're giving it a path of least resistance. It is useless to use an oil breather cap and an oil separator device because the oil separator device only works properly on a sealed system. We just chose to use a breather cap so that when the motor needs to pull air, it does it from the atmosphere instead.

We have run tests here on the dyno that shows an oil breather cap cuts nearly 80% of the oil ingestion on a high horsepower supercharged vehicle.

Hope this helps,
Jim @ JDM
 

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Noob
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Discussion Starter #13
Sweet thanks that explains a lot. I think I will just open it up with the breathers because I'm planning on hitting around 450 pretty soon
 

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Eat Springs, **** Valves
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If you go with breathers make sure you get the oil cap breather as well or you will be leaking oil like a sieve on the passenger valve cover.
 

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Noob
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Discussion Starter #15
I can't find any oil cap breathers anywhere. The other two are too easy to find, they're everywhere but I can't find the other one anywhere.
 

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Blow by is the stuff that gets past your piston rings. It's either unburnt fuel or burnt exhaust gases. If it had no way to escape your crankcase it would build up enough pressure to blow out engine oil seals (or as previously mentioned, dipsticks). In the old days they just would have a couple of one way check valves and would vent that stuff through a couple of baffles right out into the engine compartment. Then the EPA cam along and said we can't do that anymore.
So along came our modern PCV system. That blow by stuff now gets sucked back into our engines to be burned in the cylinders. It does a good job of keeping the air cleaner. Now there a couple of drawbacks to this. It is dirty air and it displaces clean air which can better support the combustion of fuel. Less fuel burned, less power. It will also lower your effective octane rating which effects the amount of timing you can run.
Today's PCV system has to deal with EFI and air sensors so it cannot just suck unmetered air into the air fuel charge without consequences. It would be like a giant vacuum leak So it is run off of the vacuum from your intake manifold it has to draw air from the metered air after the MAF but before the throttle body. It also flow when there is no actual positive pressure in the crankcase. This is actually a plus. The constant flow helps remove atomized unburnt fuel out the crankcase which if it disolves in the oil, causes premature break down of your oil.
IMO the performance benefit of not running that **** back through your motor outweighs any of the pluses. Oh, another one of the draw back of our stock system is that oil/fuel mist now gets deposited into your manifold and heads and. An gunk everything up. Do a search and you can find pics of gummed up charge motion plates that folks have pulled out of their motors.
Anyways, breathers are just the old school way of venting the crankcase. Installing them is a cinch but also has it's drawbacks. The odor of the blow by can enter the cabin and may bother you. I happen to like the smell as much as an uncatted exhaust. Just smells the way cars used to when I was a kid. You can also run a hose from your cam cover to a remote mounted breather and remove the fumes from the vicinity of your cabin air filter/intake Another drawback can be some oil drips from your passenger side breather. When you install breathers the flow of blow by only escapes from your passenger side cover. Since this is a small opening it sometimes has some velocity and oil will start to soak the breather. As more oil gathers there it becomes saturated and drips. That is why you see an oil cap breather on my car. It gives the pressure another way to escape and slows the velocity and thus less oil mist collecting on the filter. This pretty much eliminated the oil drip issue. I also change the passenger breather every once in a while because it will eventually get oil soaked. You don't ever have to swap the drivers side because it really just sits there and looks pretty. The PCV or one way check valve is actually built into the inside of the cam cover. Ideally, and I will do this to my laser etched Ford Racing covers when I get them, you should dremel that thing out of there to make both breathers functional.
Now, breathers are not smog legal so they will never pass a visual inspection but will pass where it is only an OBD check. So running a catch can is an option which will reduce, but not totally, the oil mist issue gummy up your intake tract, but you are still displacing clean air with exhaust gases.
So that is the basics and the pros and cons of the different ways to deal with crankcase pressure. IMO, breathers are the best way to go, and they look old school.
 

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Bob The Mo'fukkin Builda!
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could the oil getting onto my spark plugs be because i still have the stock pcv system in place. my car runs like crap until it gets hot and burns all the oil off. also it will run very badly if i am hard on the gas and then a quick decel similar to what jim of jdm explained
 

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3v reppin'
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I run breathers on mine. I run a hose from the passenger side cam cover to a catch can that I have the breather on, so I don't get any oil mess in my engine bay. I mounted it up by the firewall. I just dump the catch can every couple of weeks.
 

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Registered
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could the oil getting onto my spark plugs be because i still have the stock pcv system in place. my car runs like crap until it gets hot and burns all the oil off. also it will run very badly if i am hard on the gas and then a quick decel similar to what jim of jdm explained
I was going to address you earlier but got pooped after typing that last post on my phone.

We never did figure out why your breather set up was causing you issues, did we? But if you have oily plugs, the pcv system could be the cause. The oil mist is going to be increased with our boosted induction systems so I could see that as a real possibility. That is a lot of oil that has to pool in your intake for it to get onto your plugs while it's sitting there. Valve guides would be the only other plausible reason as to why they are getting fouled with it just sitting there. Do you not even run a catch can? I would definitely do that if I were in your situation.
 
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