Ironhead Ok where is the oil?

[bustert]

as i brought out in another post about removing this valve, it is not a culprit in getting engine oil to the primary side. you have to remedy the problem at the oil pump. this valve largely seals by dynamic action aka windage from the down stoke of the pistons. the disk and spring are only a marginal seal at static, and yes it will leak. an engine will produce more hp if there is a slight vacumn in the c/c as it does not have to over come pressure, however, excess vacumn can cause problems in scavenging the oil from the c/c. this valve lets a controlled amount of air into the c/c (remember that the c/c vapor and oil was sent through the timed breather vave on the downstroke) along with any oil that has gotten over the disk level. the flow is not from c/c to primary. there is no advantage of removing it. the transmission on the models that use it are designed for engine oil. blocking it and going with gear oil can cause problems down the road if your c/c fills up with oil. you can always tell when the c/c has excess oil as the rear cylinder will usually smoke until the oil is scavenged out. you can also notice a reluctance in the engine wanting to run up as it is carring all of that exceess oil around draining off hp. why hd used it is a mystry to me but i guess the engineer was doing the best he could. the excess oil in the primary will be scavenged back to the engine through this valve. this debate will probable go on and so be it. to each his own. btw: on race engines, it is imperitive to not allow oil to hit the crank and that is why windage trays and baffled oil pans are used. not only can it rob hp but it can also cause crank deflection and failure.

[FourCams]

Rep coming your way Bustert. That explaination makes sense.

[IronMick]

Originally Posted by IronMick

OK, does the FM and OEM parts book refer to it as a transfer valve? or a breather valve? I am interested because it seems to me that transfering oil is not its main function, but that acting as a breather is main, and that oil transfer is an unwanted side effect??

Originally Posted by 72Iron

Part # 25075-55 Oil Transfer Valve from my OEM parts book.

Darn! I was hoping for different. Oh well, OTV is be.

[IronMick]

Originally Posted by RRB

... But I think that Mick and MDT are right about the nomenclature being wrong.

Perhaps the whole thing is an embarrassment to HD and that is why they seldom reference it or reference it improperly ...

So, a Vent from the primary to the crankcase that we will refer to as an Oil Transfer Valve.

[RRB]

Originally Posted by IronMick

So, a Vent from the primary to the crankcase that we will refer to as an Oil Transfer Valve.

Yeah, I guess, Mick. But I think, as you and MDT and some others do, that it is less about oil and more about crankcase pressure. It seems to be a bit of a conundrum. According to conventional wisdom, it seems to be an "Oil Transfer Valve" only when it is transferring the oil in the wrong direction.

Perhaps this would be a good question to ask HD, if there is anyone there these days that could give an informed answer, or would care to do so.