Worn valve guides

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korner
Posts: 3
Joined: Sun Mar 19, 2017 9:06 pm
Vehicle: 2006 Nissan Altima

Worn valve guides

Postby korner » Sun Mar 19, 2017 9:53 pm

I doubt that there is an OBD code for this, ha ha ha, but Larry Carley of Enginebuilder magazine on at least 2 occasions has stated in articles, that the above will allow "unmetered" air into the intake port. The quotes are his. I assume he meant the air intake port and thus the combustion chamber. He goes on to say that this creates an effect similar to (worn throttle shafts or a vacuum leak in the intake manifold). Either the above is the stupidest statement in automotive history or I don't know anything about air flow in the engine compartment. Valve guide seals are designed to let a small amount of oil leak past the guide seal so as to lubricate the upper end of the valve stem. Oil is not air. Even if there is improper seating of the air intake valve itself along with a loss of compression the air doesn't come from anywhere except the air intake manifold. All the air that gets into the oil sump and the upper head area and that flows out the PCV valve (or if you have a vacuum pump that gets sucked out that way) originally got there via the air intake manifold and past the mass air flow sensor which meters the air. Except for a head gasket leak , a leaky EGR valve, or the 4 systems that use vacuum such as (power break booster system, the EVAP system, PCV hose or the HVAC system); how unmetered air would get in any engine compartment if there is no leak in the air intake manifold I would like to ask Santa Claus.


korner
Posts: 3
Joined: Sun Mar 19, 2017 9:06 pm
Vehicle: 2006 Nissan Altima

Re: Worn valve guides

Postby korner » Sun Mar 19, 2017 10:06 pm

I should add that the air breather hose allows air into the upper head so as to allow an emergency escape of blowby gases if the PCV valve is stuck closed or if you are running wide open throttle. However all that air is metered because it had to flow by the mass airflow sensor at the beginning . Perhaps turbo or supercharger or nitrous setups will provide another way to cause a vacuum leak but I can't comment on them cause I don't drive a turbocharged , supercharged nor a nitrous setup vehicle.

kev2
Posts: 6320
Joined: Sat Aug 29, 2009 4:24 pm

Re: Worn valve guides

Postby kev2 » Mon Mar 20, 2017 6:12 am

Santa is enjoying a post holiday vacation.
The theory and discussion are academic - is there an issue or question we can help with?

PS: Larry Carley's statement is valid.

korner
Posts: 3
Joined: Sun Mar 19, 2017 9:06 pm
Vehicle: 2006 Nissan Altima

Re: Worn valve guides

Postby korner » Mon Mar 20, 2017 1:19 pm

Could you please explain how his statement is valid?

kev2
Posts: 6320
Joined: Sat Aug 29, 2009 4:24 pm

Re: Worn valve guides

Postby kev2 » Mon Mar 20, 2017 1:34 pm

the created engine vacuum is evident on all of the intake - from the TB to the cylinder, is all low pressure.
So if we have excess clearance on #1 intake valve - when # 4 cylinder draws down air can draw past the leaking valve guide as well as the entire intake after the TB.


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