pillagenburn

Well, oil cap fell off for some reason when i was driving - i caught it pretty quickly. Just wondering if valve cover breathers are worth looking into? I borrowed the oil cap from my Mustang, so i have a little time, i just want to see if a valve cover breather is worth getting. I hear crank case pressure can cause intake oil leaks and some other nasty problems. I know its been off for more than a day or so, and when i put the cap back on, i noticed my car wasn't quite as 'lively' as before... it seemed weird - just wanna know what you all think.

thanks!

Bastardcat

I have a valve cover breather and have not had any problems. I installed mine after I fixed my intake oil leak just in case the crank case pressure was partially to blame. However, many people do not like the idea of indroducing unmetered air into the crank case since it does not flow through the MAF. I'm debating removing mine, but for now I'll leave it on since it seems to be running fine.

1msfyter

Had mine on for over 2 years NO leaks NO problems No performance loss. It is considered "not smog legal" . It just releives some pressure off the motor.

http://www.bealer.org/bmrrad.jpg

turbo_Z

non of the air that goes through the maf ever reaches the crank case so i dont see how that could be a problem...

Injuneer

Sure it does.

The air goes through the MAF, enters a port in the throttle body in front of the blades, travels under the top "cover", out the port on the passenger side of the TB, down the hose that goes to the passenger side valve cover, and enters the valve cover. From there, it is swept through the crankcase and the lifter valley by the vacuum from the PCV valve. That's how GM designed the CLOSED PCV system for the LT1.

The air that passes through the system gets dumped into the intake manifold, and burned. It is, in essence, fully accounted for by the MAF.

Point 2... what pressure does a breather relieve? The crankcase is under controlled vacuum from the PCV system. In the event the blowby is so bad the PCV valve can't handle it, or if the PCV valve plugs, the flow in the line from the valve cover to the TB reverses flow and the vapors are sucked into the throttle body/intake manifold. Where/how does pressure develop, at least in a reasonably healthy engine?

1997rblckSS

so the air that travels in the hose from the TB to the passenger side valve cover is going into the Valve cover from the TB??
I thought it was the opposite, I thought that vacuum that is created goes from the passenger side valve cover into the throttle body? just curious..

turbo_Z

ok i see how it would be metered but most guys that install beathers end up removing the PCV valve and plugging up that hose from the TB to the valve cover.

also, dont the pistons cause vacuum in the crank case just as they do in the combustion chambers?? so if you removed the PCV system and didnt add any kinda of pressure relieve wouldnt that cause some problems like oil leaks? im not trying to disprove you.. im am trying to understand.

EDIT: nevermind i see what you are saying about crank case pressures... should always remain constant.

shoebox

An engine with no PCV and a breather on the valve cover is just like the days before any emissions regulations. There must a vent of some type (even old engines had this). Vapor pressures could not escape if it were completely sealed and there would be seal problems, as you suggested.

chasmanz28

keep the oil cap on, my friend "had" a breather and you could always smell fresh oil coming from the engine due to that very mod, its more than pressure that causes oil leaks

GreenbeanZ28

I like my breather. Its shiny and purty! And have had no adverse affects from it.

95 Silver TA

I got mine from this place:

http://www.metco-inc.com/valvecvr.htm

It fits nice an snug and cleans up the engine pay a little too.


Hope that helps,
Claude

av8er

This has been an interesting thread. I have had a valve cover breather for a long time. In fact I cant seem to find my OEM cap anymore. Anyway, with 110,000 miles on my LT1, some of the vacume lines are in need of replacement.

What I get from this conversation is that I can remove the PCV valve and related pluming as long as I leave the breather in. I am already !EGR, !AIR and !cats. I would very much like to continue the engine bay clean up and save from having to buy new lines.

Any thing negative about this other than possible oil vapor smells?

JeffA

Injuneer

I have seen a lot of people add breathers, but I haven't seen many people delete the PCV valve.... except maybe the people who think the plastic elbow on the passenger side valve cover is the PCV valve. Combustion creates water. Water vapor that gets into the oil can cause sludge. The "positive" flow out of the crankcase, caused by the vacuum through the PCV valve helps get the water vapor, and other stuff that will form acids in the oil, out of the crankcase. Relying solely on a breather, with no PCV valve is not very smart. Most of the gunk is going to stay in the crankcase.

Some people will replace the PCV valve with a line into the side of the headers on race engines. The exhaust passing over the connection creates a vacuum and "educts" the vapors from the crankcase. One way to do it, but not real practical on a street engine. All-out race engine will feature a vacuum pump to pull the crap out of the crankcase, and create a vacuum to improve ring seal. POSITIVE crankcase ventilation is a good idea. Even before someone invented the PCV valve, the crankcase was vented by a "draft tube".... a pipe that stuck down under the car and permitted the air passing under the car to "educt" vapor from the tube.

Do the pistons create vacuum in the crankcase just like they do in the cylinders?... not really. For every piston that is moving up in the cylinder, possibly pulling a vacuum, there is another piston moving down in the cylinder, moving air and vapor into that space.

You aren't going to damage anything with a "breather". Just keep the PCV valve, or you will do invisible damage to the internals with contaminated oil.

av8er

That makes good sense. How about leaving the PCV valve and it's vacuum line to the throttle body but eliminating the line that runs from the throttle body to the passenger valve cover (with a breather filter installed)? Wouldn't this also help reduce the chances of getting oil into the intake and throttle body?

JeffA