Teeny Weeny Filter BOOM

[sil80drifter]

this is a custom intake related question. On top pf the valve cover for the 89-90 240Sx (and of the 91-94 as well) there is a little opening from which a hose leads directly into the main air intake tube. I have seen people who unplugged that tube and instead put a small air filter on that opening ont he valve cover. Since I am making my own intake tubing, to do that would mean less holes for me to drill, and I'd be all for it. BUT my friend told me it is bad for the engine in the long run and that it may cause detonation (motor blow up), althogubh at first there will be no signs of anything wrong. Anyone know why? To my knowledge that tube either sucks in clean air or dumps extra air into the intake tube, so putting on a little filter wouldn't harm the engine. anyone know of this predicament?

sil80drifter

[MaineExport]

All of the valve covers have this breather. As far as I know it is just to ventilate the head.... I don't see why it would cause harm. If there is some reason I'd like to hear it as well, because I know of A LOT of people who use the little breather filters for all kinds of different purposes.

[sil80drifter]

anyone? ANY ideas? suggestions?

sil80drifter

[fuzion]

Im pretty sure it takes air from the engine that is "fumey/oily" and passes it to the intake to burn again

after a while it leaves oil residue in the intake manifold, mine is still hooked up, but when i did my head gasket i blew the intake manifold out with brake cleaner, all kinds of oil and shizat came out

i believe its more of an emissions thing than anything, on my probe (it was forced on me), i disconnected the two breather tubes and put some filters on it from kragen, not too long after one of them was saturated with oil and other crap from the engine..

hope this helps, and if im wrong .. screw you

[C-Kwik]

All that does is take excess pressure inside the block from blow-by gasses and recirculates it back into the intake. It is recirculated for smog and for the very small possibility that it can cause a fire by venting air that has some oil particles in it. It is mostly an emmissions concern though. Venting has no ill effects on the motor, and in fact, is better if it is vented. Oil has a lower threshold for detonation and the motor would be more prone to detonation if you routed it back in. While venting the crankcase air won't really add any power in that of itself, but could allow for some more extreme tuning(leaner mixtures, more advanced timing, higher peak cylinder pressures) since it will be less likely to experience detonation.

[Silvia007]

I heard it keeps a vacuum inside the valve cover to help the pistion rings fit snug around the cylinder walls or what not. As for Positive Crankcase pressure, that's the job of the PCV valve.