How much crank endplay do you feel on prop, IO 360

[garytex]

I'm trying to understand what a baseline is for crank endplay on the IO 360s

I just put two new cyl. assemblies on,  and the engine has gotten very tight to turn when hot after shutdown .  Cool it turns normally.  Also it takes a massive effort and several tries to get a very small movement, maybe one or two thousandths, little clunk, clunk out of the prop as you push and pull on it. There have been whispers of possible main bearing or thrust bearing problems  resulting from lost bearing preload during the cylinder changes as a possibility,  said whispers having come from some very smart old engine geezers. 

 I've also heard from a guy with a factory new engine experience the exact same symptoms.

 There's no metal in the filter and analysis indicates normal break-in wear. 

Could some of you share with me what your crank and play feels like when you push and pull on the propeller, how much movement you think you get, how hard you have to pull back-and-forth on it to get that movement, please?

i'd really rather not put the two old jugs back on and/or split the case to try to figure out what's going on with this motor,  and I'm thinking about flying it some this weekend, but a little worried, if I really do have a bearing problem that would stink.   I intend to circle over the airport with my son's skateboard helmet on. :-)

 Thanks everybody, Gary 

 

 

 

 

 

 

[goterminal120]

You would be god like if you can feel a two thousands inch play.

 The different metals that make up the cylinder walls and piston expand and contract at different rates, so after warm up there may be more friction until the rings get seated. Evan on higher time engines there tighter when hot. Ever wonder why your prop stops in the same position every time.

If you not leaking or picking up a vibration, stop pulling on your prop and don't worry about it. 

[mike_elliott]

If you took more than one cylinder off at a time before replacing and if you turned the prop (crank) while the cylinders were off, you could have rotated a main bearing some. If this is the case (get it?) you better not fly it until you make sure you are not about to spin a bearing. Those thru bolts hold the case and bearing halves tight, and if you violated this integrity, you could end up with a real dangerous problem.

[N201MKTurbo]

The old wisdom is if you can't get any end play you have a spun bearing. It usually takes a good hard push and pull to get it to go. It will usually move a bit easier after a few in and outs. this is starting to sound dirty...

[Guest]

If the bearing saddles inside the case were fretted and you installed new cylinders which were torqued you may have pinched the crank bearings.  If this happened your prop would be harder to turn.   If you loosen the case through bolts at your new cylinders and the prop becomes easier to turn you'll be pulling your engine.

Clarence

[N601RX]

It's item 506, .009-.026".    In addition to what Clarence said I remember seeing a lycoming service bulletin that described a method of attaching weights to the prop a certain distance from the center and verifying the "torque" required to move the prop did not change more than a small amount with the throughbolts loose and then torqued.  

Also the bearings would have more clearence when hot while the Pistons would have less.  If the problem is only while hot then that might suggest the Pistons don't have enough clearence to account for them expanding more than the cylinders  

The service bulletin I mentioned above was sb272a.

Edited September 26, 2015 by N601RX

[garytex]

  Thank you all for posting,  that's not just a pro forma thank you, I really appreciate it.

The prop is only hard to turn when the engine is hot.

Go, yeah that differential expansion  is certainly one of the suspects. And yes you sure can feel a couple of thousands. You don't really so much feel it rather the deceleration of the prop as it starts and mostly stops.

 Hartsell says that the 15 or 20 pounds of pressure we can put on the base of the prop can damage it, I think they are per usual FOS  about that, slow go push and pull on your prop  bases, you'll feel it go clump clump back-and-forth .

Mike, the spun or possibly slightly cocked main bearing is the  Monster Under the Bed that I have been worrying about for a couple of weeks.   My mechanic only did one jug at a time,  but my understanding is that on relatively high time engines and mine has 1500 hrs. it's still possible.

 Another part of the issue is my airplane got hailed out and if I wanted to I could total it, and I would have 55 gees to go buy another airplane.  So if I got a spun bearing I definitely want to total it.  But buying another 50-year-old airplane is a fairly scary proposition and this is the devil that I know,  and have spent a bunch money bringing up to standard .

N201

 That's exactly what it feels like,  really hard to get the first little clunk and then slightly easier.

But nowhere near as easy or as much and play as is usual, and I wandered around the airport pushing and pulling on the  propellers of friends airplanes for a while

 Yes Clarence, i've been wondering about both a pinch  bearing , and a cock  bearing , and a bearing that got loose if/when the bearing  preload was lost.

 I flew the engine six hours with the outof round jug, There's no metal in the filter after six hours  The oil filter held a tiny little bit of iron powder and a very few little flakes of aluminum. No copper, ( thrust bearing )and oil analysis did not show high tin levels which I would expect out of a bearing.   I'm bamboozled,  thinking that I should suspect these over choked jugs to be the culprit, but really afraid of a spun bearing .

601rx

 That's a very interesting observation about the difference between torqued  and untorked through bolts. As I was considering the different diagnostic tools one of them was to try minimum core versus maximum torque and see how it's fun. The other one was to work over the two original jugs, ( they failed the wobble test, one of had 40  Thousand slop in the valve to valve guide clearance ) put them back on and see how it did.

 But that's about a three to $4000 test and I'm not sure I want to do it. I'm really thinking I'm going to go fly around for a while, stay damn close to an airport, and see what happens.

 

 Gary

[PTK]

Here is a nice webinar on the subject:

http://eaavideo.org/video.aspx?v=4411846372001

Edited September 26, 2015 by PTK

[Piloto]

Did you check the CHTs for the new cylinders? And the piston ring gap when inside the cylinder when installed. A low oil pressure at idle is a sign of a worn out bearing.

José 

[garytex]

 Piloto,  thanks for weighing in, the out of round cylinder ran very hot, it's replacement runs with the rest of the cylinders.  Ring end gap at the top and the bottoms of the cylinders are within spec.  Oil pressure seems about right.

[Guest]

Gary,

There is no thrust bearing in your engine.  The front surface of the forward crank throw rides on the inside surface of the front bearing saddle in the case.  This of course has a film of oil keeping the parts from contact.  

Copper in the filter shows up after the lead Babbitt on the crankshaft bearings wears away exposing the copper layer.

Clarence

[garytex]

M20DOC

  So that surface would be floated on an oil film when the pressure is up, with the engine running, and not after shutdown.  So then why would the engine turn easy cold?  Not to say that disproves the pinched bearing theory, as those symptoms are what led the engine overhaulers to both say "pinched/cocked bearing".  How would stress there shorten crank endplay.  I certainly have almost none.

I'm really bamboozled about this one, and not sure I'm willing to pay either of the prices to get to the bottom of it.  I can go fly the airplane, and see if it fails or i can split the case.  The chicken way out of this one is to total the plane and go shopping, but then I give up a particularly fast airframe, and have to navigate all the 50 year old airframe purchase issues.

[jetdriven]

If there is a pinched or cocked bearing that worn metal will be in the filter and it would be very easily noticeable.  Pull the filter at 5 hours and wash it.  If there's no copper, lead, tin flakes et.al. Go fly the heck out of it.  It's a tight cylinder and will wear in.  

[Guest]

Gary,

I'm not sure it's as dire as it sounds, certainly flying it until it fails would not be an ideal troubleshooting method.  If the troubles started after the cylinder replacement this is where you should start, I would loose the through bolt nuts and see if the crank turns easily, if not then I'd pull the cylinders for inspection and measuring.  

If the piston/ cylinder wall fit is wrong to the point that when the engine is hot the crank is stiff to turn, there should be evidence on the piston skirts..

If there is a pinched bearing on the crank journal, the crank would be hard to turn and because of the pinch you will have a hard time feeling the normal crank end play.  I'm not sure if when the crankcase is hot the bearing bore expand or tighten.

Clarence

Edited September 27, 2015 by M20Doc

[rob47v]

Gary,

I'm not sure it's as dire as it sounds, certainly flying it until it fails would not be an ideal troubleshooting method.  If the troubles started after the cylinder replacement this is where you should start, I would loose the through bolt nuts and see if the crank turns easily, if not then I'd pull the cylinders for inspection and measuring.  

If the piston/ cylinder wall fit is wrong to the point that when the engine is hot, the crank is stiff to turn, there should be evidence on the piston skirts..

If there is a pinched bearing the the crank journal the crank would be hard to turn and because of the pinch you will have a hard time feeling the normal crank end play.  I'm not sure if when the crankcase is hot the bearing bore expand or tighten.

Clarence

Winner I'm with M20Doc. Check your piston to cylinder clearance, I really don't think you have a loose bearing. Not that this doesn't happen but I find it unlikely. Pistons tend to grow with heat, if the clearance is out factory specs on the tight side, then is the engine will be hard to turn once hot!! 

[garytex]

• Yeah, the smoking gun points to the cyls.  I think that just flying it may be the thing to do.  The damn thing still scares me.  I think that its because the times I have been truly screwed by a motor/vehicle/boat, in the post mortem it was always discovered that there was more than one thing wrong.  I've had to walk miles through the dark through known man-eater territory on top of smokinging hot lion tracks in Tanzania, been trapped offshore, 96 miles offshore in a 23 foot boat, had to walk  miles back to the ranch house in 100df temps when recalcitrant engines wouldn't run.  And each time, thought "don't do that sort of stupid crap ever again"  There'se the rub.
• Thank you all for your expertise
• Gary   

[rob47v]

• Yeah, the smoking gun points to the cyls.  I think that just flying it may be the thing to do.  The damn thing still scares me.  I think that its because the times I have been truly screwed by a motor/vehicle/boat, in the post mortem it was always discovered that there was more than one thing wrong.  I've had to walk miles through the dark through known man-eater territory on top of smokinging hot lion tracks in Tanzania, been trapped offshore, 96 miles offshore in a 23 foot boat, had to walk  miles back to the ranch house in 100df temps when recalcitrant engines wouldn't run.  And each time, thought "don't do that sort of stupid crap ever again"  There'se the rub.
• Thank you all for your expertise
• Gary   

Here is a piece of advise. Don't fly it get to the bottom of this first. Too tight of piston to cylinder clearance will cause or can the piston skirt to galled causing catastrophic failure. Maybe its the ring gap either way I would look into it!!! I just got redoing all my cylinders and all well. If I may ask is it std bore, chrome cylinders, or nickel?  

[garytex]

Brand spanking new Lycoming angle valve kits, which are salt bath nitrided (Melonited) with15 thousands choke, (which is considered excessive, however LYC has NO spec for choke on assembled new cyls.)  Overhaulers have a spec for overhauled cyls, -- 8 to 10 thou choke.  The top and bottom ring end gap clearances measured and in spec.  Which BTW are 7.5 thou at the top, and 45 to 55 thou at the bottom.

 

[rob47v]

.015 choke is excessive, .010 is still a bit much but would work alright. .008 would be best and is what I imagine a new cylinder to be. On choke barrel piston to cylinder clearance should be btw .018-.021 loose at the narrowest and widest points. the .0075 max  difference allowed at the  top of piston travel, from what ever the measurement was on bottom. Choke cylinders is old technology I use straight barrels their easier to setup and deal with. Just my 2 cents and run cooler also, tho they will use a bit more oil, they also last a heck of alot longer. Ring gap on choke barrels should be new .045-.055 as you mentioned I hope.   

[mike_elliott]

  I can go fly the airplane, and see if it fails

Don't do that. Emergency room, Operating room and recovery are far more expensive and hurt a lot more than pulling a muscle reaching for your wallet to get it fixed properly.

[garytex]

Rob, I think you may very well be right, and that it is insane that Lyc has no choke spec. and 15 is stupid tight.  There is lots of room for foul language in this one. 

You too Mike, I don't wanna go, I don't heal up as well now, I see no need to seek additional excitement.  

OK, so here's the plan.  I'm too chicken to fly it, so we're going to overhaul the old cyls. and run it, see if the engine is still tight.  If so, total it, (which I can do as it has hail damage: this whole nonsense started because the engine was talking to me, and I wanted to make sure all was ok before I went to paint.  Two cyls failed the wobble test) if not, take it to paint.

[rob47v]

You might want to look into nickel cylinders. I would if it wasn't that my cylinders had less than 400 hrs on them. Nickel acts like chrome as far as wear resistants, but break in like steel. Without the oil usage of chrome that is. Well worth it in my opinion.

[cujet]

Quite a bit of speculation in this thread. If I were to guess, I'd guess that it's cylinder related. But, I'm not there to troubleshoot. 

On my Lycoming IO-360, I have plenty of end play, always. However, shortly after shutdown, the engine is markedly harder to "spin over". If I listen carefully, I can hear a zzzzzzzz noise from the cylinders. Not an air leak, but a slight scrape. I overhauled the cylinders, and the clearances are on the "loose" end of the acceptable spec. Even so, they are tight just after shutdown. 

Used oil analysis results show no problems, no high wear metals and compression remains at 78/80. It's been 500 hours of this, without any issue. 

Speculation in my case: Pistons don't cool as fast as the cylinders, leading to a period of time where clearances are tight. 

[jetdriven]

Don't do that. Emergency room, Operating room and recovery are far more expensive and hurt a lot more than pulling a muscle reaching for your wallet to get it fixed properly.

everyone is assuming it's broken.  12 grand later he may well have the exact same thing.  Cut the filter. It can't be a tight bearing if there's no copper or tin in the filter. 

[Andy95W]

everyone is assuming it's broken.  12 grand later he may well have the exact same thing.  Cut the filter. It can't be a tight bearing if there's no copper or tin in the filter. 

I'm with Byron.  Check the filter, check the screen, check the torque on the cylinders.

Consider checking the new cylinders for dimensional conformity. After that, keep an eye on it.