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Bruce Tuncks

hydraulic lifter down on power

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There is a Jabiru at our club which has good compressions on turnover, but it only develops about 2700 static RPM. The owner says it is well down on power.

 

Could it be that one or more hydraulic lifters are not allowing the valves to open properly?

 

What should I do to check this engine out? Any suggestions will be gratefully accepted, as I have no experience with hydraulic lifters. My starting point is that they were a mistake, but this is no help to the owner.

 

...Bruce

 

 

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There is a Jabiru at our club which has good compressions on turnover, but it only develops about 2700 static RPM. The owner says it is well down on power.Could it be that one or more hydraulic lifters are not allowing the valves to open properly?

 

What should I do to check this engine out? Any suggestions will be gratefully accepted, as I have no experience with hydraulic lifters. My starting point is that they were a mistake, but this is no help to the owner.

 

...Bruce

Do a leak down Bruce , that should give you some idea where to start . I don't suppose he has changed the prop lately by any chance ?

 

Bob

 

 

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If leak downs, plugs, rotor caps and leads have not been checked then that's the first port of call! The rotors on these like to come unstuck and wobble on the shaft, also they tend to corrode fast. If the basics have been done and it is passing the checks then you could indeed have a dodgy lifter, you can check lift at the rocker arm itself I cant remember the figure. All it takes is a minute bit of crap stuck in the plunger valve and the lifters go soft and don't provide full lift, effecting cam duration as well.

 

 

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If that was happening there would be a lot of "clicking " going on. The lifters can pump up and cause a loss of power due to valves not seating. They can also run out of clearance. When the lifter has no oil in it it should still have a set amount of slack usually about 2.5 mm This when it bleeds down. This is the range that the hydraulic lifter operates over. When it fills with oil it locks and regulates the clearance, eliminating the need to adjust the tappets (in theory). Nev

 

 

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Have you tryed fresh oil , ?

 

Check also if theres any play ( slack ) in the rocker arms ,

 

On TDC there should be no gap at the tappet clearence .

 

If there is , they could need bleeding ,

 

Mike

 

 

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I would be looking at fuel as well. Restricted filter, carb issues etc.

 

Make sure that the manifold hosing is secure. A small leak will effect performance quite dramatically.

 

 

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Thanks for all the helpful comments guys. Armed with these and a study of the manuals, I turned up as planned on Saturday do do the job, starting with the leakdown test.

 

Then I found that the owner had taken it to a professional guy during the week and had been convinced that a leakdown was too dangerous for an amateur on account of how you could get hit with the prop.

 

Not only that, the owner has flown it again and now says the power is ok again anyway even though nothing has been done except for the running time.

 

Oh well, it was 40 degrees on the ground and a perfect gliding day with 12,500 ft thermals and nice shady clouds, so I flew the Libelle. And now I am better informed about those hydraulic lifters. I was planning to report on what I found with that engine, but this will have to wait for another time.

 

regards, Bruce

 

 

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High oil pressure can make the lifters pump up. Maybe the hot day will lower the oil pressure. I don't like Hydraulic lifters any time. I very nearly crashed as a result of one not pumping up in a Continental 0-300 engined C-172. Nev

 

 

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Bruce , not sure what to make of this , but stand by my earlier advice ..... ie. to get a leakdown test done . Injuries have occurred to persons when doing the test, usually the result of them not understanding the forces at work and/or not following the correct procedure. Some people should realise their limitations and take their concerns to an L2 , but I can assure you that done correctly it is quite safe , and is the correct starting point to diagnose the cause of soft compressions . Also to assume that a hydraulic lifter is faulty, is flawed . Many other conditions eg. stuck rings can give similar symptoms .

 

Bob

 

 

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A compression test is not particularly useful to check hydraulic lifters. IF they aren't doing their job, unless one or more has run out of travel which can only be checked by leaking the oil out of it. and determining that the correct range of travel is available. Not a particularly easy thing to do. Also if they are holding valves partially off the seats due to pumping up it will only happen with the engine running.

 

I don't wish to detract from the value of a compression test in other matters.

 

Yes the prop can hit you hard enough to injure you. You should probably strap or clamp it securely in the correct position. TDC. Nev

 

 

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Just to throw this into the ring I have a first hydrolic lifter 2200 engine with the shevy lifters done a bit of brain nutting and found i could strip the hydrolic lifter and machine a plug and insert it into the lifter making it solid. I replaced the rockers for adjustable ones and last I sent the push rods to Camit to be shortened by about 4 mil I think. All works well so far but remember the rockers are left and right for each cylinder. Bill from Bunderberg gave me a set of rockers when checking the rockers ended up with 2 right handed rockers thanks Bill again for the rockers. I bought one from Jabiru wow cost me about $50 bucks for one no adjuster. So reverting back to hydrolic lifters can be done at an affordable cost and camit will sell the kit for around $1000 I think.

 

 

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Hyundai, I believe that engines with hydrolic lifters have a different camshaft profile to accomodate the properties of hydrolic lifters. Did you get any advice as to wether you need to change your cam.

 

 

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Hyundai, I believe that engines with hydrolic lifters have a different camshaft profile to accomodate the properties of hydrolic lifters. Did you get any advice as to wether you need to change your cam.

Sorry I should have also said the early first hydrolic lifter engines still had the solid lifter cam. Cheers

 

 

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Where did the hydrOlic come from? It's hydraulic.

 

re the cam profiles some of them were so wrong the lifter edges were taking the load. ( but that's a separate problem). Nev

 

 

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DazzaI am new to this site what is your quote (I give up) ????????

Dazza may be just a bit confused. The latest engines are apparently hydrolic i.e. they use water for lubrication.

 

 

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Hi my J400 has never pulled more than 2700 revs static but will go to the red line flying even with the Jab prop I have a 3 blade revolution prop and it will rev higher on the ground but only if it is pitched "fine" I have set it so that the static revs are as per the Jab prop.All good with the engine.(Solid lifter).

 

Cheers Rory

 

 

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Mine is similar , 2750 static , 3000 rpm flat out 3500 amsl ,hindered by old pusher exhaust .

 

Thats hyd./ lifter 3300 with a 62"dia. X 54 " pitch ,

 

Runs well although pushed a bit of oil out the overflow bottle breather on the the last 4 hr run,

 

Ive just taken it off the run in oil and onto 15/50 ,

 

Im wondering if the multi grade oil is creating more blow by ?

 

Ill try the W100 and see if it makes a difference .

 

 

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If the owner thinks it is down on power, I assume that it has run better in the past. Going to an expert and them running it for a while while not finding anything wrong sound like a recipe for a future failure. I havn't ever seen an engine that exhibited problems and then came good being reliable. About the only fault that would self heal is poor quality fuel, anything else would tend to come and go. So find out what is wrong where a failure will be safe.

 

 

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Dazza may be just a bit confused. The latest engines are apparently hydrolic i.e. they use water for lubrication.

Dazza

 

You really should get a life.

 

 

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Guest Andys@coffs

Re 15W50 mutigrade vs W100 (plus is good!) Id talk to your local Jab guru (Wayne Johns? from memory in your neck of the woods) I seem to recall that most of the senior maintenance guys don't think that greatly of multigrade and have doubts about its ability to last full term for an oil change....

 

But check...

 

 

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