Hot rear cylinder example Jabiru 3300A-2575 and plenums

[facthunter]

 You may assemble it that way but the idea is give it enough operating range and it will take care of itself till the heads need overhaul. The cam profile is also not as it would be if operating "solid" as it will if it bottoms.  It's to do with "quietening" ramps on the solid lifter set up with tappet clearances. The hydraulic lifter operates with NO lash. Nev

[Bruce Tuncks]

I reckon you should have more clearance( with no oil in the lifters) . I understand Nev's point about the pushrod coming loose, but I would think that you should be able to use at least 1mm of movement before this happened.

If you don't do this, you are effectively saying that you think the hydraulic lifters are too unreliable to cope with. 

[RFguy]

1mm at the lifter is probably OK, corresponds to about 1.7 mm  at the valve stem.

[Jabiru7252]

Are all these mods legal? I'd only ever want a fully experienced and qualified mechanic (LAME) doing that sort of work.

[facthunter]

I wonder how many of them (Engine qualified) would specialise on Jabiru's or want to. Checking settings are in a specified range is not too out of the ordinary.  A "certified" version would have to be more black and white.. As I see it at initial  assembly the stipulated figure would have to be achieved. It's easier to  check then as there's no oil in the lifter. Nev

[Bruce Tuncks]

The only lame I actually know is quite slow. I'm sure that there are smart ones out there, and I have met some of these, but all  their experience was  Lycomings or Continentals, put into standard GA planes like Cessnas. They were out of their depths on some non-standard ( by Cessna standards ) parts of the son's Lancair. ( The retract hydraulics are marine stuff on the Lancair)

I have never even heard of a lame who gets to the bottom of things like rfguy and facthunter. These guys are quite professional .

The lames  also suffer from the " get it out the door" urgency which you probably need to make money these days, and so they do not have the time to think things through so well.

I don't want to be seen as denigrating lames, in another life I could have been one.

[RFguy]

That's the thing Bruce, a L/AME fixing a customers' plane cannot make it a research project !

 

 

[kgwilson]

I've seen plenty of really dodgy repairs done by so called professional lames especially electrics with poor joins and a bit of insulation tape, a Mooney engine installation the flange was almost touching the  cowl & needed shims, routing of fuel lines close to hot exhausts, screws missing, etc. I don't trust anyone to do anything on my aircraft except me.

[facthunter]

it's JUST another job to them. It's YOUR life to you. You are more motivated, obviously. If it's above you skills and knowledge base get help. Never be too proud to ask some one who KNOWS. Not always a  recent GURU.  Nev

[Bruce Tuncks]

yep, the great thing about maintenance, as opposed to flying, is that you are not pressed for time and you can ponder and seek advice all day.

 

[RFguy]

So. spent some time yesterday on the engine  after doing 6 circuits around noon in the Brumby.

 

#1 had one clearance at 0.25mm, the other 0mm. removed the lifters, and the two  roller hydra lifters have VERY different recess character.  the one with clearance pushes in a long way, and has a distinctive feel like the others with good clearance.  The tappet without clearance, that lifter feels quite different, sticky and doesnt have a distinctive stop feel. . partially disassembled that lifter, seems empty of oil. 

 

Have brought home that lifter to figure out how to disassemble and inspect.

 

The rear pots 5,6 with recession, those lifters appear to be OK, its the recession causing some of the trouble I think. Push rods are all 207.00 +/- 0.03mm. the Jab book says 217/215mm. maybe another  typo... or did they mix up numbers with the gen4 manual, does it have different length pushrods I wonder. anyway, we'll see. 

 

have the rods from 1,5,6. they appear to be machined down and press fitted heads on them.  looks like some soft (ally) block clamps made up in the press will remove the end.

-glen

[facthunter]

  Push rods...Put one end  in a chuck and use a slide hammer effect on the other end. Grip against the steel end pieces.   With the lifter, There's usually a circlip holds the lot together. Thin one. Nev

[Markdun]

Glen, I’ve a couple of new roller lifters at my hanger if you want to experiment with them....guaranteed empty of oil.  I could also pull some pushrods....but I haven’t measured them.

[RFguy]

thanks Mark, I'll see how I go  today/tomorrow , might have a bit of a sniff on this lifter today. I removed the clip and half the insides at CWR, have it on the bench for further dissassembly.  There is certainly two very different behaviours I am seeing, and I want to know why, at least before I start chopping pushrods.