Exhaust gasses coming OUT of valve cover

[robftw]

I've known my valves needed adjusting for a while now, however today i changed my intake setup to use a filter ontop of my valve cover.

Driving i had HUGE amounts of exhaust coming through the holes in my fire wall / shifter hole (i have no boot)

When i looked at the engine bay and revved the engine, i saw the exhaust come shooting out of the filter.

I'm assuming this is because i need my exhaust valve adjusted correct? and not nothing seriously catastrophic.

[Zforce]

Make sure your pcv valve is working, if it is you could have excessive blow-by. Are you running the stock air filter ? was there any oil in the filter housing ? oil in the filter housing is a sign of blow-by.

[robftw]

Make sure your pcv valve is working, if it is you could have excessive blow-by. Are you running the stock air filter ? was there any oil in the filter housing ? oil in the filter housing is a sign of blow-by.

oh i need to add this, its a 76 280z Fuel injected, I do not have a PCV valve

[robftw]

ACtually is the PCV valve on the bottom of the intake manifold? if thats what you're asking about i "might" have one, i never looked.

also i had oil in my AFM when i removed the hose coming from the boot, to the valve cover

Edited June 29, 2011 by robftw

[cozye]

yes you do.

[Zed Head]

today i changed my intake setup to use a filter ontop of my valve cover.

Why did you do this? Did you have to adjust anything to get the engine running decently afterward? Unless you blocked the PCV port you would have a large leak in your intake system, probably requiring at least some idle adjustments just to keep it running.

Seriously, wondering what the purpose of the change was...

The exhaust coming out is "blow-by", typical on older engines and one of the gases the PCV (Positive Crankcase Ventilation system) is designed to remove and burn.

Edited June 29, 2011 by Zed Head

[robftw]

I did not have to adjust anything to get the engine running differently, it actually ran better without the vac leaks coming from the old boot. Keep in mind most of the emissions systems on my car have been removed.

looking back, i never noticed if i had a PCV valve, This picture shows the crank case hose it looks like it might have one on it. http://4.bp.blogspot.com/-ZcHPumE9nv0/TcSfQhggSbI/AAAAAAAAAMw/-V3O2imZe-0/s1600/WP_000568.jpg

Here is a picture of the changes i made, i believe the car used to have a T fitting for the cold start air valve / valve cover but it is missing, the air valve hose routes back to the intake manifold..

[Arne]

I hate those little valve cover filters, for exactly this reason. They don't stop blow-by from getting out and smelling up the car. If it were me, I'd plumb that breather back into the intake system somehow.

And the blow-by could definitely be worse if the PCV is clogged, so you may want to change it too. I seem to recall they aren't very expensive.

[beermanpete]

The PCV valve pulls the blow-by gasses into the intake manifold. At large throttle openings there is not enough vacuum to pull in all of the blow-by allowing some to escape out the breather vent in the valve cover. This is why you see some smoke come out when you rev the engine.

Your comment about oil in the AFM, combined with the excess blow-by suggests worn or stuck rings, not out of adjustment exhaust valves. Your best short term solution is to restore the original connection from the valve cover vent to the intake boot. This will keep the smoke and fumes in the engine and out of the cabin.

[FastWoman]

^^^ What the snail said! Nissan describes the reversal of gas movement in the FSM's section on the PCV system (EC section). Under load, the PCV system doesn't suck up all the blow-by, and so it blows back out from the valve cover to the intake boot. Under low throttle and high vacuum, fresh air goes from the intake boot into the valve cover, down through the engine, and out the PCV valve into the intake manifold.

[robftw]

Okay i'll have to tap into the new air intake then.

Also my car does have a serious tapping coming from the no. 5 cylinder thats why i'm 90% sure its my valves

[beermanpete]

Okay i'll have to tap into the new air intake then.

Also my car does have a serious tapping coming from the no. 5 cylinder thats why i'm 90% sure its my valves

The tapping and possible need for a valve adjustment is an unrelated issue/problem, but clearly in need of attention.