Valve Cover Vent

[atkinson40]

Is the vent on the top of the valve cover that is tubed over to the carb supposed to suck or blow air? TIA Kevin

[izzo]

Its supposed to blow air, but not a lot of pressure. It hooks into your carb for emissions or w/e. But ideally you can just put a filter there, or run it into a catch can.

[banzai510(hainz)]

@ idle they blow air for sure.

 

Dont know at High RPM but if alot of blowup then those vents can spray oil past the baffle. I just run a hose down past the trans.

 

But the crank case vent blows out at idle and sucks in when reved up.

[atkinson40]

Thanks All. Mines blowing out, but I remember reading some where here that if it wasn't correct it could be bad valves or some other problem. -K

[datsunaholic]

It's an INLET vent. But at idle there's not enough circulation nor vacuum on the PCV to pull. I've had a couple cars (both NAPS-Z) that did draw air in at idle. If it's blowing oil out the top vent you have problems, I've seen some L-series that did but have never actually had that issue on any of mine. A little pressure at idle is OK, a lot is usually blowby from worn rings.

[datzenmike]

My old L20B I put my finger over it and after a while it would hold it there.

[ggzilla]

It depends on the engine, year and model. Some datsun engines it is inlet, others it is outlet.

 

Venting with a hose is OK, but connecting it to the PCV valve is better, as it will ventilate the block. Lower oil consumption and lower pressure loss. Side benefit of lower emissions too.

 

 

Yes, if your rings are worn, too much blowby will get past the pistons and pressurize the block. This can cause the PCV valve to gunk up or overload, so some guys disconnect it and just use a vent hose. Better is to repair the engine.