mrblob

mrblob

Well Known Member
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I'm nervous about the answer to this question...

In September, I bought a freshly overhauled engine from a guy that was selling off a project. He had the engine built by a shop in Reno in March, and to date, the engine has not run since it was built. Came with new logs, which indicate a number of new and overhauled parts, new gaskets, seals, bearings, etc.

While working on my install today, I noticed that the crankshaft has a bit of play, both in and out (normal), and up and down. Is a small amount of up/down play normal? Acceptable? I've been searching google all afternoon, and can't find a straight answer. Best I can figure from the Lycoming overhaul manual is the main bearing tolerance is pretty tight, which wouldn't let the crank move up/down a perceivable amount. But maybe I'm misreading it.

I'm feeling kind of depressed at the thought of having to tear down my "new" engine. Thoughts? I called the shop that built it, but they haven't gotten back to me yet.
 
You shouldn't be able to move it up and down. Forward and backward, yes, a little. Up and down/side to side, I don't see how that is possible without something being way off.
 
It's deceptive

The end play is kind of deceiving, it can look and feel like an 1/8" or more but when you dial it, it turns out to be just a few thousands. The radial play should not be felt at all, its in the neighborhood of .001-.002", I'm guessing and hoping you are feeling the end play again.
Good luck.
Tim
 
... sigh...

I went out to the hangar and measured it. I used a caliper to measure the difference (relative to a reference on the case) from the at-rest position to the highest position while pushing straight up, perpendicular to the crank. .016" That's a lot. Any ideas? I'm guessing this means pulling the engine and cracking the case (ugh...). Are there different thickness main bearings? Maybe it has the wrong one.

Hopefully I can get in touch with the engine builder tomorrow. More importantly, hopefully he'll warrant his work.
 
Ya....unfortunately It shouldn't have anywhere close to that much vertical movement. Your going to have to split the case and find out why. Wrong bearings I suspect.
Just be happy you found it now, and not while in the air.
It will be a great learning experience, so read up.....
 
Hmm...

It's hard to imagine having that much play even if you have a .006 under crank with std bearings. I still wonder about your method of measuring it. The engine shop should have records of what went in it including the yellow tags. If they did screw it up it really makes you wonder about the rest of the work.
Good luck.
 
Maybe thin wall bearings where they don't belong? Looks like you do get the "opportunity" to explore your innards. Do you have tags on any of the machine work? New parts list?
 
engine builder

I spoke with the guy that built the engine. On the up side, without hesitation, he agreed to open the engine and fix the issue. He also agreed to do it with me standing there, and to ship it back to me at his cost if he couldn't get it back together in time for me to drive away with it.

On the down side, he didn't sound as concerned as I would have expected about the slop. He acknowledged that it was too much, and needed to be looked at, but his initial reaction was along the lines of "yeah, it'll have some play, these engines are kind of sloppy." Makes me nervous about getting it fixed to my satisfaction.
 
You shouldn't be able to move the crank up & down. If there's a noticable movement, then something is wrong (case dimensions, bearing sizes, crank over ground, etc.).

If not yet run, disassembly is probably what I'd do. You should probably try and get a copy of the Lyc overhaul manual and table of limits - there are a number of specific dimensions that should be rechecked (both measured and checked back to the associated paperwork that you have).

That it has not yet run makes the job easier. However, there are a number of areas, although not rocket surgery, still fall into the category of "don't try this at home." If you have reservations about the person offering to help, you might want to ask for some additional eyes on assistance from someone who has done this before.

Dan
 
Crankshaft play

Calipers are not a satisfactory means of measuring. Before you go any further find someone to measure this with a dial indicator clamped to the crankcase.
I cannot come of with any combination of wrong bearings that would allow the amount of play you are measuring. The difference between thin wall and heavy wall main bearing thickness is approxinately .070, which would equate to .140 total play, or slightly over 1/8". It appears that is not your problem. Standard bearings on a .010 under crank also does not compute.
The manufacturers minimum and maximum clearance for the crankshaft in the main bearings is .0011 to .0041. Service limit is .0050.
Regarding "don't try this at home", why not? Buy a video, study the overhaul manual carefully and have at it. These engines are very simple.
The only problems I have had with engines I assembled myself were cylinder problems, only on Continentals, and accessory problems.
I have had many problems over the years with near new factory Lycoming engines.
The vast majority of the so called engine shops are really just assembly shops. All or most of the parts go to specialty shops such as Divco, Aircraft Specialties Services and ECI to name a few. These are the true engine overhaul shops.
 
I borrowed a dial indicator from a mechanic on the field, and measured everything again. The vertical movement at the point where the crank exits the case is .014". I'm not sure what's constraining the movement at that amount. It could be the crank seal that's limiting the motion, and possibly have more slop at the bearing.

I'm going to take the engine back to the builder, and watch over his shoulder as he goes through it. That way it'll be on his dime if the case needs to be sent off to be line bored or something. It's a bit of a set back, but at least I'll be able to find out if there are any other issues while we're in there.
 
Paul after you get the case split make sure he does a proper clearance check on the main bearings, well all bearings for that matter. First you want to install the main bearings in their respected places in the case halves. Next you want to bolt the case halves to gether per the lycoming overhaul manual and torque to the specified quantity without the crankshaft installed. Next take a dial bore gage and check the internal diameter of the bearing bore openings with the main bearings installed; record this number for each bearing location. These should be very close to the same number. Next take a micrometer and measure the crankshaft at the each respected bearing location. The micrometer needs to be locked at each bearing location so the measurement can not change while you take the micrometer to the dial bore gage and measure the internal diameter of the micrometer with the dial bore gage. The difference between diameter of the bearing bore openings in the case halves and the crankshaft diameter is the main bearing clearance. This is the best way to achieve the most accurate clearance figure. Plastigage is a useful option but not quite as accurate. You can check the rod bearing clearance in the same manner. Send me a pm if you have any questions. Best of luck and do please keep us updated.

Bill
 
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measuring

For those who don't have access to micrometers and dial bore guages, a simple way to do this is with plastigage, available in many auto supplies for just a few dollars.
 
I met with the builder today and cracked the engine open. The crank measures standard. The bearing bore in the case on the other hand was off. With the bearings in place, and the case halves bolted together, we measured 0.010 clearance, which is way too much. That doesn't add up to the 0.014 motion that I measured, but taking it apart and bolting it back together along with removing the lever of me pushing up on the crank could account for the other 4 thou. At any rate, the builder is incredibly embarrassed and apologetic, and we're both glad I found it before starting the engine. He's sending the case off for overhaul (or replacement if its fubar).
 
Knowledge is power

mrblob said:
I met with the builder today and cracked the engine open. The crank measures standard. The bearing bore in the case on the other hand was off. With the bearings in place, and the case halves bolted together, we measured 0.010 clearance, which is way too much. That doesn't add up to the 0.014 motion that I measured, but taking it apart and bolting it back together along with removing the lever of me pushing up on the crank could account for the other 4 thou. At any rate, the builder is incredibly embarrassed and apologetic, and we're both glad I found it before starting the engine. He's sending the case off for overhaul (or replacement if its fubar).
Click to expand...

Paul,
Sorry, but today is the first time I spotted your thread. Fore and aft end play can be an issue with Lycoming crankcases. Service Instruction 1354B addresses this issue. Service Instruction 1377 deals with problems with the crankcase bore. Lycoming has released several Service Instructions which deal with crankcase issues and the proper procedures to repair them. It is possible that the crankcases were repaired previously. I'd like to send you a copy of SI 1112E, SI 1225D, SI 1290F, SI 1334A, SB 212B, and SB 238.

SI 1123D also applies IF you have an older, "narrow deck" engine. SI 1417 is pertinent if you have a "dual" magneto engine.

SB 201E, SB 475C, SB 505B & SB 530B, SI 1111 & 1205 will interest you, as they deal with crankshaft issues.
Reading these tech documents will greatly aid you when you watch the mechanic reassemble your engine. I'll contact you off list to co-ordinate sending these tech documents to you.

Charlie
PS A few of the above mentioned documents are available for download from Lycoming at

http://www.lycoming.textron.com/support/publications/index.html
 
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Two screw ups?

This whole thing smells funny, I wonder if the case was reworked at all during the rebuild. There should be a yellow tag if it was done. For the machine shop to line bore it that far out of tolerance is unlikely, and as others have mentioned, checking the machine shops work at assembly is standard practice. To just throw it together without making these checks is just sloppy work or worse, dishonest.
Maybe I'm just cynical, but for the amount of money and risk to life involved with this, I'd be hopping mad.
I do hope you get it done right the second time, and I would suggest you collect all the yellow tags and parts invoices for documentation.
Tim
 
Charlie,
I look forward to the documents. Thanks!

Tim (and everybody else who shares his feelings),
3 weeks ago when I found the problem, I was spitting mad. There were definitely corners cut. I have yellow tags for the cam, gears, cylinders and some other parts. I have receipts for the pistons and a number of other new parts. There was no documentation for the case. I don't think it saw a machine shop or a mic before assembly. I made it pretty clear that I didn't trust him and insisted that I participate in the disassembly and have an opportunity to verify all his measurements. He was accommodating to my requests and also brought one of his employees in on the weekend to help get it done faster. He didn't offer any excuse except to say he screwed it up, should never have let it out of his shop, and would make it right. The case is being shipped to ECi for overhaul.

The rest of the engine looked very good inside. I think I will have a properly overhauled engine in a few weeks when I get it back.

I also called the fsdo. We agreed that if he makes me whole, we chalk it up to "stuff happens" and if he doesn't, they're ready to pay a visit to his shop. The supervisor didn't think I'd get a very warm welcome this weekend if they went to see him first.

Right now, I think things are looking up. I'll follow up again when the engine goes back together.
 
Bob I'm glad you have found the problem before it was too late. Best of luck on the rebuild. So long as you keep a eye on the assembler and he confirms and checks all clearances and he supplies you with yellow tags of all critical parts you should be good to go.

Bill
 
Wow! I'm a little surprised at your FSDO's reaction. They are generally not in the business of getting involved in your commercial dealings with a repair station. I would think they'd be more interested in why essential steps were not taken at the initial assembly.
 
Oil preasure

For such a simple engine Lycomings have a ton caveats,Ad's,Sb's,Si's to name a few. There are only four shop's in the world that do this work,Three of which are required to stamp a work order number into the case half's at overhaul and may still have a record of that service.My understanding is it's a one price service around $725-$735 depending on who you talk to,$3500 to replace with a serviceable one if unrepairable. Given what you found I would go over every component with a fine tooth comb,you would of had little if any oil pressure and would have chucked a rod before you left the ground.Important question.Does this engine have a log book?Is there a data plate installed on the sump?Where did the core come from N#,or parts off eBay?Is this a new limit or service limit engine?If you can't get the yellow tags or 8130's Get copies,Take lots of photos.The true cost of building these engines is getting the parts on a bench,paper work ready to go.The assembly is the fun part
 
Engine Tear Down

You might have mentioned this already and I missed it; but this is a great time to copy downall the numbers of the various parts if you don't have that already. Might also be a good double check against the "paperwork" you were provided with initially...

doug
 
Forward aft play

With the case open. Put the shaft in with half the case
Lying on the table. Check the fore and aft measurements
Of play in the shaft where it hits the case. This measurement
Tolerance is addressed in the overhaul manual. Pm me if you need
This explained. Went through the process recently with an 0320.
 
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Runout

With half the case on the tabel and the crank in position with main bearings, it is also a very good time to check the runout
On the flange using a clamp on thousandths gauge.
 
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