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Jabiru rocker oil pressure fix

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wb2ssj(at)rochester.rr.co
Guest

Posted: Sun Mar 11, 2012 3:41 pm Post subject: Jabiru rocker oil pressure fix

Check out these two links - 

Gentlemen, please  view the below items. This is a problem that has been noticed on two of engines  in my area. One is a 2200 and mine which is a 3300. It seems to be with early  hyd/lifter engines. Any comments welcome. 

 Tex

 

http://contrails.free.fr/engine_jab_rocker_lube_en.php

http://contrails.free.fr/engine_jab_rocker_lube_fix_en.php



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selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Mon Mar 12, 2012 1:51 am Post subject: Re: Jabiru rocker oil pressure fix

Hi Tex,



What exactly is the problem you are having, uneven oil feed, valve guide wear, something else?

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Cheers, Selwyn
Kit 66 VH-ELZ

wb2ssj(at)rochester.rr.co
Guest

Posted: Mon Mar 12, 2012 2:45 am Post subject: Jabiru rocker oil pressure fix

The problem is extreme wear on the exhaust valves, as shown in the video. 

The amount of oil seems proper, but it enters the head nearest the intake 

valve. The exhust valves get less as its farther down the stream. Its the 

same on 6 cylinders.

Tex



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info(at)flylightning.net
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Posted: Mon Mar 12, 2012 5:06 am Post subject: Jabiru rocker oil pressure fix

Not correct Tex.  On the previous 3300 heads the first oil feed slot is

closer to the exhaust valve in two of the six cylinders, equal in two

cylinders and closer to the intake valve in the other two.



Pete Krotje

Jabiru USA Sport Aircraft, LLC

931-680-2800

www.usjabiru.com





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selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Tue Mar 13, 2012 3:12 am Post subject: Re: Jabiru rocker oil pressure fix

Hi Tex,



I don't know about this one.  I looked at it a while back when I was just getting towards flight ready but couldn't convince myself that it was worth doing anything.  



Bearing in mind that all the heads are the same then the relationship between valves and oil feeds varies from front to back and from side to side so if you are getting similar wear patterns on all six then its possibly not oil feed.  If there is oil in the rocker boxes then it is going to be splashed about by the rockers, springs and everything else thrashing about so I can't see anything is going to be dry.  Also, given the temperatures involved I'm not sure how far oil would get down the exhaust valve guide, maybe someone can comment on that.



The responses to venting the rocker boxes mentioned in the first link seem a little unusual to me given that Jabiru say that the rocker boxes are under negative pressure.  



Effectively in the six cylinder there is a gallery which runs through the heads fed by two oil pipes from the block with two outlets in each rocker box and sealed at the front and back of the engine by small welch plugs.  Each rocker box also vents through the pushrod tubes.  All this should mean that there is not much differential pressure between the boxes which means that there should not be much reason for differential feed and good opportunity for any oil which gets into the gallery to be distributed along the engine.  It doesn't seem to me that its all going to run out one end or the other but it is possible I guess.



I suppose the mod to the oil feed plugs in the crankcase to increase oil flow as in the second link would be easy enough but I think I would be looking elsewhere.   I guess it is possible that there is a dodgy batch of valves or guides out there.  If oil supply is the issue you should also see the effects on the rocker wear face where it contacts the valve and in wear on the rocker bush / shaft although wear in the bush seems to be pretty much the "normal" condition.



Sorry if this is a bit of an unfocussed ramble but I hope it is some help.

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Cheers, Selwyn
Kit 66 VH-ELZ

wb2ssj(at)rochester.rr.co
Guest

Posted: Tue Mar 13, 2012 3:47 am Post subject: Jabiru rocker oil pressure fix

Selwyn, thanks for your reply an I am sure that its just oversized guides 

that were installed in the engine. I seen the burnt area around the exhaust 

values the first time I checked the heads. And its the same on all cylinders 

which makes me think its not the amount of oil reaching the valves. Its just 

leaking around the guides. Will keep you posted on what is happing and again 

thanks for your reply.



Tex

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