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i kno there are some threads on this already but im hearing like a bajllion different answers.........

so i was wondering if it was ok to disconnect this hose that connects from the head of the motor to the intake pipe and stick on a filter breather or such.......what do you guys recommend i should do.




also what oil should i use??? my car has about 80,000 miles and i've been using 5W-30 synthetic.....i heard i have to use heavier oil cause of the high milage........help please
 

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As long as you plug the hole in the intake pipe where the vac line use to connect you should run fine, your car will smell a little worse and you'll fail emissions if they inspect your engine bay where you live. If you don't plug the hole in the intake pipe your car will be getting un-metered air and run like poo.
 

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Wow, what's with all the breather threads all of a sudden?

You shouldn't fail emissions, and it will not smell any different. It's not like you're removing the cat. That is the FRESH AIR side of the PCV system. It draws air in that side, and the dirty air goes out the PCV valve side (drivers side valve cover). You put a breather filter on the passenger side valve cover because it's drawing in air on that side, and you don't want to be sucking in dirty air.

You should not fail emissions if the breather is on the fresh air side (except maybe in California, because you modified the emissions system). Any inspector who knows cars would know the difference. You would fail if it was on the PCV valve (dirty) side, and putting a breather filter on that side would be stupid anyway. Part of the reason the PCV system works how it works is because the PCV valve is hooked to the intake manifold, and it uses the vacuum of the manifold to draw out excessive crankcase vapor and pressure. If you disconnected the PCV valve side from the manifold and put a breather on it, then there would be no way to draw out that vapor and pressure and it would just float out of the filter. Then, you would get vapor on both the fresh side and the PCV valve side.

There is no performance gain by putting a breather on the valve cover and plugging the intake pipe. You either do it for looks or because your intake pipe doesn't have a nipple on it for the hose.

Nate
 
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There is no check valve on the fresh air side so it doesn't always take air in it will also vent air/oil vapor out. There is a slight performance gain as removing this from the intake will keep the intake air cleaner. However you will now be venting this into the air under the hood which is why your car will smell a little worse, and you will fail a visual emissions inspection (at least in PA, in addition to CA).

You could also put catch cans, or inline air/oil filters on both the Breather and PCV lines to achive the same result without venting to the apmosphere.
 

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There is no check valve on the fresh air side so it doesn't always take air in it will also vent air/oil vapor out. There is a slight performance gain as removing this from the intake will keep the intake air cleaner.
I disagree. There is a slight performance LOSS!

The head went from operating in vacuum (less pumping and windage losses) to atm pressure.
 
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There is no check valve on the fresh air side because there doesn't need to be one. And the PCV is not really a check valve, it is more of a variable valve. It should never fully close unless there is a backfire in the intake. Let's go over how this works:

Under partial throttle, the valve is opened more (less vacuum to pull the valve closed) so crankcase pressure and the fact that there is more vacuum on the PCV valve side causes any blow-by and moisture caused by combustion to go out the PCV valve into the intake manifold.

At WOT, there is almost no chance that some vapor will escape out the fresh air side since the valve is now fully open (0 vacuum pulling on the valve) and manifold pressure is just below atmo pressure (contrary to belief, at WOT the manifold pressure is just below atmo, since the engine is still drawing air in). Even though the pressures are still close, monifold pressure is still lower than atmo, and combined with crankcase pressure it will tend to flow out of the PCV valve. Vapor out of the fresh side won't happen unless you have a lot of blow-by. If you have lots of blow-by, the crankcase pressure would force air out both sides because the slight difference between atmo and manifold pressure isn't enough to overcome crankcase pressure. Residue build-up around the fresh-air side would indicate vapor, which would indicate excessive blow-by.

When you let off the throttle, the throttle closes and the vacuum pulls the valve to it's most closed point (which usually isn't fully closed). Since the fresh side is before the throttle plate, there is no way for it to draw vapor through the fresh side because there is no vacuum being created in the intake pipe. Since there is no combustion at closed throttle, there is not enough blow-by, and no vapor to collect.

Unless the system isn't working properly or your engine is in really poor condition or under boost, you should never see oil residue in the intake pipe or anywhere before the throttle plate, period.

I've run breathers on my last 4 cars and have yet to see vapor come out of the breather, I haven't had any problems with it smelling more, nor have I had problems with oily residue anywhere around the breather. Even on engines with excessive blow-by. Why? Because my PCV system works properly and all of the vapor goes out of the PCV valve like it's supposed to.

The only exception to this is on my boosted engine. There is so much blow-by under boost that it will force vapor out both sides, so it would force air out of the breather. I fixed this by hooking both sides to the catch can and tied the catch can in to the turbo inlet.

Nate
 

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haha i plug mine with a dime and a gasket made of duckdtape. then lots more duckdtaped to keep it there. i check on it every time im under the hood. the dime is so perfect in size its not even funny. as far as the breather went i just kind of wedged the hose somewere... i did this before i went to the races one day. talk about irish rigging...
 

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The head went from operating in vacuum (less pumping and windage losses) to atm pressure.
Hadn't thought of that, but it sounds correct. +rep

If you have lots of blow-by, the crankcase pressure would force air out both sides because the slight difference between atmo and manifold pressure isn't enough to overcome crankcase pressure.
On my previous car I had a breather filter and it behaved like I described in my earlier post (it was a 1.6L inline 4) I didn't have high oil consumption and compression tested 180-184 across all cylinders (it had a problem that turned out to be a sticking IACV, and I compression tested it while trying to figure out what the problem was). Anyway what I'm saying is your desc of how a CVS works is accurate so I think the only difference might be that some cars have better CVS than others, so some might end up with a little oil/vapor out the breather.
 

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Wow, what's with all the breather threads all of a sudden?

You shouldn't fail emissions, and it will not smell any different. It's not like you're removing the cat. .....You should not fail emissions if the breather is on the fresh air side (except maybe in California, because you modified the emissions system)...Nate
Nate he is in califorkupnia.. like me, he'd defiinitely fail the visual. Having the crank case vent to atmosphere is an no-no here.. :(
 

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i switched over to Mobil1 10w-30 High Milage on my last oil change, but Im just over 100,000
You're in GA, you don't need that! The first number on oil, in this case 10w, is for the cold winter startups, its regular operating temperature is what the SAE 30 is for.
 
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