Cracks me up umbrella flutter, what do u think it's designed to do(flutter).

 

I have to clean my K&N filter every 3000 miles or it will begin to drip oil on my cam cover. When I asked the dealer they told me.... This is normal and they all do that. This only became an issue after they did the stage 1 mod.

 

The guy tunes engines for a living. Not saying his opinion is it but until I hear some factual and proven reasoning then I have no basis to go on other than the stock design. And yes they are designed to flutter but maybe its a timing issue? Again I don't know. Im only adding what I recently heard to the thread.

 

So educate me here. Folks that do this are just re-directing where the air is vented. Its still being vented.

I dont understand how venting outside vs back into the throttle body could cause the umbrella flaps to flutter.

So this is a sincere question - I would like to know why a tiny amount of vapor going into the throttle body prevents fluttering umbrella flaps, while redirecting that outside does. Please explain what happens, exactly.

 

Seems to be common in modified engines. I did the basic stage one being a free flowing air cleaner and exhaust along with a PCV. I've been fortunate not to have the issue so far. Maybe that's what they are referring to? Modify things and it slowly trickles down to having to modify other things to compensate? I really don't have any good answers.

 

Hey Man, I cant answer it as I don't know either. Never claimed to know. Maybe it has to do with the suction from the intake?

 

Poppet valves (another name is umbrella) are one way valves. As the pistons come down pulling in a charge of air and fuel from the intake, underneath pistons in the crank case, the air is compressed. It drives thru the right crank bearing into the cam galley and upward thru the push-rod cover into the valve cover were the rocker arms and valve springs..ect are. It pushes thru a felt baffle and out the poppet valves into the air filter box. There the actual air is drawn into the air flow into the intake. Any oil falls out and goes to the bottom of the OEM air box. If it's a SE open type filter, you will get a few drips thru the filter since there is nothing to catch it.
When the pistons go back up to compress the air and fuel, they create just as much return air that sucks back into the valve cover. So you get a load of dirty air into valve cover.
Also, there is a small vent hole in bottom underneath the baffle box with the felt filter. Drilling this hole out only lets the air thru the baffle box blast thru from the bottom increasing the oil flow to the air box.

 

Pictures.....please, and Thank You!

 

Great explanation.

Thanks RIPSAW

 

Hey all,

OP here. Thanks for the replies and breather excerpts/info.

After viewing the breather info provided by ripsaw, I still don't see how any significant amount of air gets sucked in past the umbrella valve during piston upstroke, if the umbrella is in good, operating condition. I'm guessing any flutter in this valve is at best, momentary, when the pistons transition from downstroke to upstroke. I'm no expert in these motors by any stretch of the imagination, but unless there is some other air passageway effecting umbrella operation that I am unaware of, it doesn't seem likely that any significant amount of air is passing the umbrella during piston upstroke and hence allowing dirty contaminated external air from entering the crankcase. Again, all this given the proper operation of the umbrella.

With that said, it seems that the decision to vent crankcase air to atmosphere via an open tube or with a tube/filter, involves determining what is best overall for these motors. That being knowingly allowing dirty/oxygen-depleted crankcase air back into the throttle body, vs. trusting the integrity/operation of the umbrella valve and an external vent tube to effectively bypass the AC/throttle body. If taking the latter option of venting externally, I assume this requires another maintenance procedure of periodically checking external vent tubing for evidence of suction while the motor is running, and for evidence of discharge of condensation and possibly small amounts of oil from the crankcase. With no evidence of suction at the external vent tube, can one assume the umbrella valve is operating as designed, and that external air is not being sucked back into the motor via the external vent tube?? If that be the case, then there is little potential for engine damage related to the umbrella valve.

So, if the umbrella valve and external venting is operating as desired, I see the potential for more harm to the engine by allowing dirty, oily air into the intake, resulting in carbon/gummy pistons and valves vs. taking the decision to by-pass the AC and vent crankcase air elsewhere.

Again, I'm no expert, but I'm all ears if someone can provide physics-based or mechanical reasoning behind a preference for routing crankcase air back into the throttle body. I only want to do what's best for the longevity of my motor, given the cost of engine rebuilds.

Lastly, I will likely switch to a larger ID tubing for my crankcase venting, and perhaps attach a small filter to that tubing (for concerns of environment and umbrella valve failure).

Opinions/feedback welcome. Thanks all...