Run in oil after piston ring change

[G-OMER]

I am going to fit a new set of rings to my number 1 cylinder jab 2200, due to a 65/80 leak down, suspected stuck rings while i am doing a de coke on all 4. I also intend to fit new exhaust valves at the same time to all 4 motor done 500 hrs.

 

What are the thoughts about changing the oil to a run in oil because of the new rings? And what grade to use? Im in the UK and currently run 15/50 aeroshell, would it matter for these, cannot see at the moment the benefit, does it help with the bedding in? How long does it take to bed in?

 

Cheers

 

Gary

 

 

[jetboy]

have a serious talk to Roger over there - if you are replacing rings you want to hone all bores out to the new limits and fix the base nuts issues if you have any - and make sure you get them torqued NO loctite and heated evenly. if you are going to this amount of trouble consider doing all the rings.

 

And be wary about what valves you are changing too the Chinese ones dont have as much horse as the UK ones - your choice -

 

My opinion, based on real experience of an O-200 new cylinder set which got 'run in' on normal aero oil and then required all rings replaced, fresh honing and a hard run-in on straight oil, to fix the issue, best to use S80 or S100 oil for at least 50 hrs.

 

Ralph

 

 

[G-OMER]

I bought the valves from skycraft, i am replacing the barrel with a fully serviced unit from Roger, i also bought 2 fully serviced heads as well, so at the end of the job I will have all these parts available for the future or if any one else wants them

 

 

[jetboy]

I had a look at the skycraft pictures. they look like the Chinese valves, if they have the square section stem grips rather than the earlier 'half round' grips, then please tell us , when the two collets are fitted to the stems, do the collets have a clearance in the gap, and are the valves free to rotate within the collets clamped together?

 

Nobody around here seems to have the new valves fitted - except me - and what I saw seems at odds with what Jabiru are saying in their latest service advisory on failing valvegear.

 

Ralph

 

 

[Dieselten]

Use a non-compounded aviation mineral oil such as Aeroshell 100 for the first 50 hours. This will ensure the rings are fully bedded-in. Run the engine at high BMEP by cruising at high power and low altitude for the first few hours, and vary the power from time to time to heat and cool the cylinders to assist bedding in.

 

I ran my rebuilt Jabiru 2.2L engine in at 2900-3000RPM at 1500 feet amsl for the first 5 hours after the rebuild. It cruises nicely at 2900RPM now. I used the straight mineral oil for 50 hours after the rebuild to make sure. Now I run Aeroshell W100 only and change it every 25 hours, with the oil-filter changed every 50 hours.

 

The additive pack in the 15W50 is worn out in the Jab engine in 25 hours or so because the Jab engine has very little oil in it for an aircraft engine. No matter what oil you use, change it every 25 hours because it is pretty much finished by then, especially if you use Avgas.

 

Oil is cheap, and it is the life-blood of your engine.

 

 

[facthunter]

Jetboy, the matter you draw attention to is scary. Bad collett groove dimensioning is bad news. They should match the valve and leave a gap when installed . You should always tap the end of the valve a few times to make sure the colletts are seated.. The Jabiru needs the best exhaust valves available....We already have two kinds of gudgeon circlips possible. We are building problems for ourselves. (Murphy's Law). Nev

 

 

[jetboy]

Nev,

 

can you be a bit clearer about what youre saying.

 

Its my understanding that the original valves, pre 2009, have the semicircle section collet / stem grip grooves. these collets meet without gap, allowing the valve stem to suspend loosely and able to rotate when opened.

 

Now they changed the valves and collets to a different type in 2009. the ones they supplied me , when fitted, had a residual gap with the collet halves gripping the valvestem firmly. I assumed they know what they doing when they make these changes. I didnt like it but all the valves come from a different supplier now.

 

I say these are the valves which dont rotate. I emailed them about this, after the advisory was issued due to 2 cases of washers wearing thru and dropping valves recently.

 

I'd actually be worried if these new valves do rotate, given the square edges on the grip. no thanks, i'm staying with the round gudgeon pin clips too!

 

Jabiru say they do rotate, if not the collets are faulty.

 

So who is correct, did I get a faulty batch from them? The engines been running 140 hrs since, so I think I might have assembled them correctly. has anyone else seen their collets in action? I will have another look when doing the tappets

 

Ralph

 

 

[facthunter]

Fine. I don't like the valves that are free to rotate in the collets. Cleveland Fords have had quite a few grooves ( multiple) mince up and fail and they put it down to that. I'm not sure the faulty ones were genuine.

 

. Some valves are designed to rotate in a positive way. This evens out some distortion and helps even wear. This is done by designing the spring to move the valve in a rotating sense incrementally, so it slowly turns, as the valves open and close. Jabiru haven't incorporated this feature and may not even know of it, but it would probably be a good idea

 

I have never seen a valve that the collet doesn't sandwich it tightly under the influence of the taper ( unless it is a very old motor where some used parallel collets) This requires that a gap exists in the collet where the edges meet. I wouldn't trust anthing else myself.

 

Round gudgeon clips work better if there is a small chamfer around each end of the pin. With this feature the clip tends to be held in the groove rather than being pushed out of it if the pin moves against it. You can't use a clip where the ends are turned in .

 

The "seeger" circlip ( square section) has to have the right depth and face placed as in the Jabiru instructions. Apparently they have had some "faulty" circlips that are not firm in the grooves. If this happens the loose clip can wear lots out of the piston groove and come out , and muck things up properly. You should always check that the clip doesn't rotate too easily due to insufficient tension. Nev

 

 

[G-OMER]

I had a look at the skycraft pictures. they look like the Chinese valves, if they have the square section stem grips rather than the earlier 'half round' grips, then please tell us , when the two collets are fitted to the stems, do the collets have a clearance in the gap, and are the valves free to rotate within the collets clamped together?Nobody around here seems to have the new valves fitted - except me - and what I saw seems at odds with what Jabiru are saying in their latest service advisory on failing valvegear.

 

Ralph

Attached is pics of the new valves, the collets close completely around the valve and the valve rotates within the collets, these came from skycraft UK there is a step just below the collet were it looks like the last bit has been machined down as smaller dia than the valve shaft

 

 

 

[jetboy]

Thanks Gary I don't recall the valves they supplied me having any machined down area

 

It will be interesting to see which type last the best

 

BTW your collets look upside down in the picture or is that the Northern hemisphere version

 

 

[G-OMER]

Well spotted, i just slung them on for the photo to check for a gap

 

 

[G-OMER]

I checked the old ex valve from the spare heads i bought and the collets completely close around the valve, now this motor has not had the valves changed, its serial no is towards number 2000, waiting for the exact number, i got 2 complete heads, 1 barrel and 1 complete piston with rings and pin. My original plan was to drop 2 and put these on then drop the other 2 , im now going to drop all 4 at once, so will prob re sell these parts

 

 

[Sapphire]

I've done hundreds of top end overhauls on cars [o/h cyl head and replace rings] As long as the bore is better than 4 thou wear, you can stop the smoke and get the compression back with a hot half hour run [accelerator to the floor 60 to 100 k's top gear] Air cooled a\c engines seem to be fussy. The honing needs to be the right courseness and angle and the run in at full throttle and near full throttle. Anytime the valves see the light of day, replace the exhaust valve and the valve guide. They operate under conditions that would make dante's inferno look like the dark side of the moon.