3300A : A tale of two (hydraulic) lifters, one with no spring.

[RFguy]

In Part 2 of my refurbish thread (hot cylinder 3300...)

 

So, before I start shortening push rods, a one way trip, I wanted to thoroughly investigate why the lifters feel different when depressed manually.

And coincidently, the valves with more clearance on a  push-in, the lifter had much less spring pressure and I could generate more travel pushing in the rod (the 'soft one') .

 

The lifter with zero/neg clearance was harder to push in, much much, and I couldnt feel an end stop. ('the hard one') 

 

I removed the hard one a couple, of weeks ago, took it home, diassembled it . OK that's how a hydraulic lifter is constructed ! alright then (remember my experience is overhead cam engines) .  Went over the MarkDuns and he has some new lifters and they feel just like 'the hard one'.

 

Last wednesday , went back to plane and removed the 'soft one'.  (I'm getting proficient at getting a Jab engine apart) .

This morning took it apart-Gasp ! NO INTERNAL SPRING ! WTF ! Just air behind the piston was generating the spring pressure.

With a good oil seal, that air compartment might actually be preserved , if you are lucky... and this one clearly had preserved its seal after 400 hours. 

But anything is possible. air out, oil in, etc etc

 

Contemplating next move.

 

Edited May 16, 2021 by RFguy

[RFguy]

Hypothesis. Factory found  zero/neg clearance during assembly.... Removing the spring is one way to get more clearance (stop occurs earlier as the compressed spring is a stop) . 
Mutter mutter. Can only have been the factory.  Will be requesting springs for all the missing springs, at no charge thanks.

[facthunter]

Coil binding shouldn't act as a stop. It's the oil  supply that shuts them up . (Fills it with oil). Maybe the spring (which is quite light) only seals a hole so it will pump up. It's important to do this fairly quickly. A "NEW" motor should have the oil galleries and filter primed with oil before starting.. If you do this you will hear a lot of hissing anf gurgling them  nothing.  when the air is purged.  This doesn't mean the lifters are pumped up .It only means that it will happen more quickly.    IF you cranked the engine over as the valves individually were seated they would remove the excess Lash as the lifter filled with oil to the running  (zero lash ) condition. Nev

[RFguy]

Hi Nev

thanks for the input. - for clarity : 

At the moment with galleries empty and lifters empty, that is, a  NO pressure scenario. empty lifters :

 

the cylinders with NO lifter spring run about 0.5 to 1mm lash when pushed in - the travel on these lifters is about at extra 1mm . - 

 

the cylinders with the spring present run zero or marginally negative lash and cannot be pushed in any further (any available travel in the lifter is taken up as the head is screwed home) 

 

 

[Blueadventures]

7 hours ago, RFguy said:

Hypothesis. Factory found  zero/neg clearance during assembly.... Removing the spring is one way to get more clearance (stop occurs earlier as the compressed spring is a stop) . 
Mutter mutter. Can only have been the factory.  Will be requesting springs for all the missing springs, at no charge thanks.

Hi RF could you post an image some time.  Have not seen a Jab lifter but did a bit of time on Subaru lifters and their 0.5mm ‘o’ rings that could only get out of Japan.  Cheers.

[RFguy]

I will get a photo.. here are the insides. the plunger spring was missing

 

[RFguy]

So, the issues of running without the plunger spring in the high pressure chamber (HPC) 

 

The plunger spring is important because it ensures the chamber piston when at rest, when the cam lobe is at neutral, expands to meet the  pushrod head valve closed location.  Otherwise the initial pumps from the cam lobe, until the HPC fills with oil, will be over clearance and possibly a rod could fall out of the ball socket at the rocker in extreme scenarios.

 

The air spring in there will gradually bleed down if piston wall clearances are high, and also the air will be displaced by oil, changing the character.  The spring is required !

 

I will call Jabiru today for a please explain why a few of the lifters dont have their springs. 

 

The spring have some height even when compressed , and the lifters to bottom our earlier. So remove the spring and you get a little more unpressurized clearance.....

 

 

 

 

 

 

 

 

Edited May 16, 2021 by RFguy

[RFguy]

ANSWER FOUND

 

Jabiru , as usual Leith very helpful -says: No way, they would never have had their springs removed to make clearance. Why some don't have their springs, dunno.

But: 

And also, a couple of SN after my engine, push rod lengths were changed from 207.00 to 206.00, because some clearance problems were being found.   Mine are 207.00

So, that's the answer.... Time to shrink the rods , and add some springs.

[facthunter]

They should specify the Lash when the follower is compressed until it bottoms out with the lifter on the back of the cam. ie No oil. I would expect something in excess of one MM  (.040").  Normal action has a full hydraulic lock and no operating lash. Camshaft is made to suit this and is different to a manual adjusted tappet setup.  Good condition followers don't leak down very quickly. Dirt in the oil can change that or wear.. If I had one I'd operate with rollers but solid ones and adjust the tappets myself. Maybe they don't make a camshaft for that but it can be reground. I think they are from Crow. Nev

[RFguy]

Hi Nev

there is no spec for the roller engines... But I would think about 1mm also. 

Hey everyone, oh this gets even better : 

In the lifter that had no plunger spring. - The check ball didnt feel like the other 'good' lifter' , so I disassembled the check valve spring compartment found that spring broken into several pieces. somehow it still managed to hold the ball when provoked. The little check ball bottom cover looks like its been deformed slightly on one side, and a tiny bit of the check ball spring  is found in the bottom of the body. No marking on the lifter bore evident. the check ball spring is thin wire and tiny.

Golly

So if you run without the spring- the check ball valve cover may come adrift and float around in the bottom of the body. (the plunger spring holds it in) 

No spring and EMPTY it feels like there is a spring- you are feeling an air spring. 

geezus

 

Edited May 17, 2021 by RFguy

[facthunter]

Plenty of room for Murphy's Law to apply. Nev

[facthunter]

Are your  rockers  oil feed fed up the hollow pushrods.? Nev

[RFguy]

yes.

ran some numbers on oil pressure on the piston in the 5/8 bore, + piston spring pressure if spring is heavily compressed /nearly binding - . Ya dont want the oil pressure too high as the head valve springs on the jab are not all that heavy.  Jab did drop the hydra engine Green zone oil pressure from 525 kPa down to 350 kPa. wonder what happens when things are very coold.

 

as you can see Nev, this rework has taken me on quite an experience  ride.... 

Edited May 17, 2021 by RFguy

[Old Koreelah]

5 hours ago, RFguy said:

...as usual Leith very helpful...

That’s always been my experience as well.

5 hours ago, RFguy said:

...a couple of SN after my engine, push rod lengths were changed from 207.00 to 206.00, because some clearance problems were being found.   Mine are 207.00

Interesting. I wonder if mine (SN 3178) is affected?

[pmccarthy]

Is this where the saying “off your rocker” came from? 😮

[RFguy]

Mine is 33A-2575 August 2013, 375 hours

I dont have too much time to F around, so I ordered 12 x 205.7mm rods from a place in the USA, USD$10 each  (instead of AUD35). Since the problems are worst where there has been recession at the underside of the head on the rear cylinders, I am unlikely to use them all and will have some left over for others.

 

I'm expecting to use a minimum of 5. But if other good clearance cylinders end up being 'soft' (no spring in the lifter) they'll need replacing, also.
 

[RFguy]

After finding at least one without  the spring, and I am amazed that when the check valve cap came off internally that something didnt get bent !!!!

,( there are more, just not confirmed yet)

that, I would suggest people disassemble their hydraulic roller lifters if they have the opportunity . fish out with a prod, dont get a magnet near them.

 

Next step -

when I go back to the plane (at Cowra), when my new shorter pushrods have arrived from the USA....

 

-remap existing fully bled down clearances.

-remove all heads (again)  (they're not torqued up yet).

-remove all lifters and measure and inspect each one to confirm plunger spring present and check ball spring healthy.

-replace lifters without springs and/or damaged. 

- Fit the  shorter rods where required. this means rear two cylinders at least.(that have some recession).

- note in maintenance book each above step and result.

 

[facthunter]

Revs tend to make them pump up.(For all engines as a general  statement)  You aren't going to rev a cold  engine too much. 50 psi should be enough if the oil holes are in the right place.

  Must have got a phone call during that one. (didn't send it)

 Now, responding to the above..... Often shortening the length of the "recessed" ones restores the original geometry If this weakens the spring pressures shim below the relevant spring. Nev

[RFguy]

Hi Nev. OK on the shimming. We'll see. CYL 2,3,4 are good, but we'll see if they are good because the they were lucky , and there is no recession, or it could be they are good because the lifters have no plunger springs... 5,6 are known recessed, but again, lifters need to be inspected.   

 

 

[facthunter]

My post omitted the word valve stem. Shortening them is very common. Where hardened caps are used you may run out of thickness to the collet groove. The height the valve comes up is critical to getting minimum guide wear as you have to retain the relationship with the rocker pivot  point which is fixed in these engines.. You will probably get this all OK, but it as something you usually check with any engine. As I've said many times I wouldn't run hydraulic lifters if there was an easy way to convert it it was MY plane with ME flying it. There's a case for keeping to a known standard condition though if disposal is likely or it's used for training. Nev

Edited May 18, 2021 by facthunter

[RFguy]

OK. got it.

 

I wonder how many valve frying incidents and unexplained rough running are either hydraulic lifter issues, AND OR valves sticking open.

[facthunter]

They HAVE to be right. It's not  a matter of being "somewhere near". Very hot and stretched valves are certainly likely with the occasional valve head detaching.   Nev

[RFguy]

Hi Nev

I'm not sure in this case, why you are focussing on the stems, unless you are speaking ' in general'

 

My valve stems are all pristine. they're all OK. all motion is within normal range. the slight 0.2 to 0.3mm mm head recession  on the lower side of the rear cylinders is a very small angular error onto the rocker balls. inconsequential, IMO, the normal mating variation would drawf any angular change there. ... 

 

all I have to do is verify the lifter internals and behaviour, and put in some shorted push rods (as jabiru  went 1mm shorter than I have because  the problems I and others have )

 

Beware the book ! it  has errors/ inconsistances- they mix up the solid versus hyrda (gen2)  roller versus roller hydra push rod lengths which are all different !!!

 

 

Edited May 18, 2021 by RFguy

[facthunter]

IF your valve is seat recessing, shortening the valve stem is the way to get the geometry back to where it was, in respect of the stem top position to rocker pivot point. . At valve half open the rocker contact  area with the valve end and the rocker's pivot point should be at a right angle to the valve  stem axis to minimise side load. It's essential to have this right. THEN you do the rest. which should be made easier because of what you've just done.  Nev

[RFguy]

AHH I see the confusion 

 

I have cylinder body (steel) into (Aluminium) HEAD recession on the underside where there is little cooling.

 

No seat recession.  

 

Most jabs have it on the rear cylinders for a number of reasons. I've calculated how and why elsewhere here.