With a Shovel top end!

A given... But... Not as Forgiving as a Head Breather.. A Shovel can really benefit from Crankcase evacuation... but PITA... on any of 'em.

 

Question:... How come I've never seen a check valve on a shovel (bottom breather) but yet they Incorporated the umbrella valve on the top breather Evo?

 

Damn good Question right there... I will not put anything... nothing in the breather line of a bottom breather...Too many bad Experiences... the way I can barely Tolerate an oil Cooler on My Harley... I have one... Only because it was Original to the Model...I put Nothing in the return side of the Oiling system... [except that one]
I blame EPA and Tree Huggers for the head breathers and Umbrella valves as well..
I have very Limited experience with head breathers... and do Not think they are as Efficient as a case Breather Anyway. And I don't care if I pollute just a bit of oil Mist!!
Since Most of my experience is a result of Drag Racing..I am adapting what I feel is pertinent for street use... I am trying to Help my Head breather, Breathe, by routing to the Intake... But...No Oil in my breather system.... Yet

 

 

I believe the idea with the umbrella valves is to maintain a negative overall pressure in the crankcase.

Hence the terminal demise of all "marking territory" jokes around Harley Davidson.

 

I must say it is... I think I might have solved an issue I've been having with my stroked top breather Evo...

 

No way in hell yer Harley will even come close to Achieving "negative pressure"... tho logic tells us it may...Experience Shows it is Impossible...Best we can hope is to let 'er breath uninhibited..and trust me... it will all be Exhale!!!
And yes... the head breather would need to be pretty badly Sumped to get oil outside the System...

I bet letting a Stroker Breathe thru those Heads is gonna be challenging... Drag Racers do it completely Differently... But... We ain't racing... just want to do the best we can with what we gots...

 

Or have bad umbrella valves or damaged plastic breather...

 

No... The valves can be removed without any real change... and the breather gear??? Maybe... I never seen one so bad that it Caused sumping...But, Maybe.

 

Neither one will cause sumping but if either or both are bad you will be spitting oil out the breather tube wherever it's routed to.