bryanflood

bryanflood

Well Known Member
My engine was due for an overhaul and I thought it might be fun to do it myself. I am going to post some of the pictures and assembly steps here. I will not be able to post everything I did b/c I just didn't document it that carefully. There are many measurements and assembly steps that need to be taken, of which I just didn't take a picture, sorry.

Also, I took all the pictures with my phone, so sorry they are such poor quality. Hopefully you can get an idea of what I did.

My first day I worked on getting the crank shaft seal in place and the gear on the crank shaft. Getting the shaft seal on is a bear, it requires a special tool, for which, I paid $100.

Next is the gear there are lots of instructions in the manual to make sure that it is firmly seated on the crank. Including tapping with a punch and checking with a feeler gage, finally after torquing the screw the saftey is bent.










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Rebuilding Lycoming O-320

The rods are put onto the crank shaft in the following pics. I was really curious to try the plastic gage technique of checking the bearing clearances against a dial bore gage and a micrometer. My experience was that the plastic gage was fairly repeatable but not very accurate. The plastic gage seemed to show that the clearances were around .002 smaller than the other gages. Luckily all measurements ended up being within limits so I didn't extensively investigate which was more accurate. I guess however I trust the mic and dial bore gage a bit more as I calibrated them against standards. Finally the journals are oiled and the rods installed, be carefull with the nut orientation.







 
Rebuilding Lycoming O-320

You have to check a bunch of dimensions on the case, this is pretty boring, except that you need to assemble the case and take it back apart again. The shafts for the idler gears need to be installed. Tappets are also oiled and fit at this time.





 
Rebuilding Lycoming O-320

Before the case can be assembled the bearings need to be put in place. The front bearing is a little tricky because it's split is oriented 90 degrees to the case split and it has to be carefully aligned. Marks are made on the bearing BD case during a test fit, then when the crank is installed you can verify that the marks are aligned with those on the case. The cam is also installed in the pics.



 
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Rebuilding Lycoming O-320

Before the case is joined the shaft seal has to be prepared with contact cement and the dreaded POB and silk thread installed. This actually went easier than I expected. Next the bolts are tightened in a specific sequence to pull the case halves together. I didn't get allot of pics, things are pretty busy as there is a 1 hour time limit.




 
Rebuilding Lycoming O-320

The accessory case needs to be assembled with the oil pump and the rod for the fuel pump. The gears also need to be aligned and installed on the back on the case. The tach shaft and seal needs to be installed. Double check that all the pipe plugs for the oil galleries are in place. There are also a bunch of measurements taken at this stage. Finally the oil pump drive shaft and tach shaft are wiggled into place and the assesory case screwed to the engine.













 
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Rebuilding lycoming O-320

Next I masked and painted the case, then moved it to my living room (can't carry it up the basement stairs with cylinders installed) for final assembly. I had to build a ventilated paint booth in my basement b/c it's below 0 here. I used a marine engine compartment blower to blow the fumes out of my dryer vent. Worked great and didn't stink up the house.





 
Rebuilding O-320

The next steps involved populating the accessory case and installing the cylinders. I think I also put the oil return tubes on at this time. I will have to wait for a parts shipment before the next update, which might be a week or more.



 
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o 320

I am collecting parts for an 0 320 and intend to assemble it on my own. I have been to two assembly schools. This will be only the second four cyl Lyc I have done, I had help on the bottom end on the first one.
Comments:
If you choose to use the plastigage, DO NOT torque the rod bolts any where near the full torque value. These are stretch bolts, full torque one time and then throw them away.
I am going to put my faith in Divco on the case dimensions. I do not plan to assemble the case to check dimensions.
IIRC correctly, the crank seal is usually done after the engine is fully assembled. The special tool is not necessary. This has been discussed at length on this forum
There are three different style/part number main bearings. Doweled/no dowel and o 235 style four piece front main.
Some shops seem to do the case assembly on the vertical with the crank bolted to the engine stand. I personally don't like this and plan to assemble the case on the horizontal as shown in your pics. If assembling on the horizontal, the cam should be wired in place temporarily to the"upper" case half. This holds the lifters in place while lowering the "upper" case half in place.
The crankshaft end play should be verified after the case halves are joined.
It appears you used some kind of cam lube. Can you address this and other lubes/sealers used??
My VERY OLD Lyc manual calls for a stp/oil mix. Some shops use stp, some don't. I plan to use the stp mix unless someone convinces me differently.
I just found some very interesting info on AVWEB about oils and cam lubes etc. I have always used Aeroshell but will not be using it again.
 
The top left nut on the oil pump is safety wired backwards....;-).
Did you get the castle nut under the cam gear installed and saftied? Can't tell from the pictures.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Ditto

Ditto what Dan said. My hangar neighbor just got his cases back and all looked good but one journal was completely wrong. Had to send them back for regrind and line bore. Doesn't look like a good step to skip.....
 
Lycoming O-320 rebuild

Thanks for the comments,

I did safety the castle nut behind the cam, but I guess I didn't take a picture. I have to admit that bugger is well hidden. In terms of goops, I used whatever was recommended in the overhaul manual. The ones I remember are: POB #4, PLIOBOND, the STP mix recommended (I forget the ratio, but I think there ara a couple different ratios, with one ratio for case studs and another for lube), the cam is coated in moly lube. For cleaning I used a degreaser, some walnut shells and the standard petroleum solvents. The paint is Randolph enamel engine paint.

I don't want to add fuel to the fire and I know the old adage about only torquing the rod bolts once. But I want to play devils advocate for a minute and get the experts opinions. I don't think the O-320 uses torque to yield bolts and the repair manual seems to suport this in paragraph 7-69. It says that some bolts are "stretch length" bolts and these should not be torqued beyond the specified yield limit. The O-320 does not use stretch length bolts, so other than replacement at overhaul the manual doesn't seem to have much input. Paragraph 7-67 does say to tighten the bolts "moderately tight" before inspecting the bearing I.D.s. It is a bit vague I guess.

Bryan
 
jrs14855 said:
If you choose to use the plastigage, DO NOT torque the rod bolts any where near the full torque value. These are stretch bolts, full torque one time and then throw them away.
Click to expand...

This is why you save the old rod bolts and nuts...use those for checking your rod clearances. That way you can torque them to your heart's content then throw away when you're done.
 
rod bolts

Every thing I have read says my 0 320 rod bolts are torque one time and do not reuse. Maybe Mahlon will comment on this. I think my friend balancing my rods is doing it with the rods/bolts as a matched set. He is very knowledgeable about the small Lycomings so I'm not concerned about this. He made it clear that he will not torque the bolts to the max. I would think half the normal torque would be fine for measuring and would not hurt the bolts. I will check my engine school notes and see if I can find anything on this.
 
We use slave rod nuts and bolts to mock up the rods for machine or measurements. That being said , if you buy a new rod assembly from ECI, it comes with bolts and nuts, and they are installed and torqued. When questioned, ECI said it was acceptable to un-torque the bolts and nuts supplied with the new rod assembly and to reuse them.
So go figure....
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Bolt torque debate

I was thinking that there might be way to shead some light on the re-torqing question for non-stretch length bolts. Here is what I propose:

1. Get a new rod bolt and nut off an O-320
2. Measure it's free length with a mic
3. Torque to spec
4. Untorque the bolt
5. Repeat steps 2 through 5 10 times
6. Compare free length values. If the bolt is deforming only in it's elastic range the bolt free length will remain constant through-out the test. If the bolt deforms then the torque values are taking the bolt into plastic deformation. If there is plastic deformation its not safe to retorque. I'm not sure this test really shows anything about the nut, but that is a different discussion.
 
Bolt stretch

I performed the test I was suggesting in the last post with an old O-320 connecting rod bolt P/N: 78027 that I removed during overhaul. The bolt does not have ground surfaces on the end like I am assuming a stretch bolt would but I still got fairly repeatable readings on the micrometer. This is only a torque bolt and the torque spec for my engine appears to be 480 in-lbs. So I tightened the bolt 10 times to full torque. My goal here was to see if the bolt was deforming plastically or only elastically at the given torque. It appears from my measurements that the deformation was only elastic as it returned to the original length after each time I torqued to 40 ft-lbs. Here are my measurements after each tightening: 2.4615, 2.4615, 2.4616, 2.4614, 2.4614, 2.4615, 2.4614, 2.4615, 2.4614, 2.4615. When the bolt was tightened it stretched elastically to 2.4676 or about 0.006". Just for kicks I overtightened the bolt to 50, 60 and 70 ft-lbs and it held the torque each time without stripping the threads. I also measured the bolt length after the overtorque and got 2.4616, 2.4614 and 2.4616 inches respectively. I think this is probably more evidence that you can torque non-stretch lenght bolts more than once, although I have to admit it really doesn't take into account the nut or the condition of the threads. But it's interesting anyway.

Still waiting for parts to arrive to complete my rebuild.

Bryan

 
Finished rebuild

Well, everything took loger than expected, but I finished the rebuild and the motor is now hanging on the plane. I don't remember exactly where I left off in this thread. I ordered a couple new push rods to get the valve clearances correct. I should be starting the motor in the next couple weeks, which I am looking forward to.

Bryan



 
Engine in service

Well, my engine has been in service for more than 50 hours now and the break in period went according to plan. I just wanted to share my oil analysis results so others might know what to expect for their break in period. The trends towards less contamination of the oil seem good.

Bryan



http://www.freeimagehosting.net/med4b
 
Looks good

Having overhauled a number of air-cooled VW engines, I have always been interested in building/overhauling a Lycoming. I also built all of the engines for my Super Late model oval track car, so I am used to dealing with high $$$ engine parts.

That said, the stumbling block for me has been the inabilty to run engine on a test stand and dyno to confirm a successful build and run the engine in. My home airstrip is in a rural area. It's 2600' turf with 100' tall fir trees at the departure end.

I am interested in what, if any, precautions you felt it was necessary for you to take because it certainly looks like you had a great experience.

Larry Tompkins
544WB -6A purchased
building a -7
W52 Battle Ground, WA
 
Risk of field overhaul

Larry,

that is an interesting question. I think with any overhaul of an engine there is likely to be somewhat more risk of engine stoppage in the first hour or so of run time. This is a risk that seems to be often accepted with any engine that is field overhauled. However while test cell running does reduce this risk I don't think it eliminates all elements of risk, especially those elements that relate to some of the largest factors leading to engine stoppage such as fuel system problems. But that doesn't really answer your question.

There are specific instructions on how much time you can run on the ground before first flight and some specific temperature limitations. I was very careful with temperature limitations but the bottom line for me was that I was not going to fly until I was absolutely sure the engine was going to be producing power for at least several minutes of flight. The risks with excessive ground running according to the eci break in manual seemed to be two fold. First was glazing of the cylinder walls which can lead to high oil consumption and excessive blow by. I didn't believe that excessive blow by or high oil consumption was likely to lead to power failure on the first flight. The second risk seemed to be overheating of the cylinder head leading to scoring of the cylinder walls which was something I could inspect for before my first flight with a small bore scope.

Ground runs were specifically limited by ECI to 4 minutes each before the first flight. I probably exceeded this a couple times as it was difficult to operate the engine at the recommended ground power settings close to my hanger. I ran the engine several times on the ground mostly so that I could assure the aux systems were correct.

I was probably less concerned about the engine core than I was about the engine aux systems, but I probably had 30 to 40 minutes of ground time before I flew, which I am sure is excessive. My friend who bought a test cell engine had 1 hour on the engine but no hours on the aux equipment such as the fuel system, prop and new electronic ignition that replaced one of his mags.

I felt that carefull assembly, ground running and inspections subsequent to ground running could reduce the risk to an acceptable level for the first flight.

All of that said, I still think the lowest risk method of engine overhaul would be to have an experienced shop perform the work and run the engine in a test cell. I'm sure that many people will argue that this practice reduces risk and is the safest option, I don't disagree with this and would encourage anyone to have their engine built by a proffesional. On the other hand I was eager to build the engine for my own enjoyment and education. I think acceptance of some risk for these benefits is the same trade off that is made when building or flying an experimental aircraft as opposed to a certified aircraft. Perhaps most people would disagee with me as most people seem to prefer to put non-amateur built powerplants in their amateur built airplanes.

I really enjoyed assembling the engine.

Good luck,

Bryan
 
LarryT said:
Having overhauled a number of air-cooled VW engines, I have always been interested in building/overhauling a Lycoming. I also built all of the engines for my Super Late model oval track car, so I am used to dealing with high $$$ engine parts.

That said, the stumbling block for me has been the inabilty to run engine on a test stand and dyno to confirm a successful build and run the engine in. My home airstrip is in a rural area. It's 2600' turf with 100' tall fir trees at the departure end.

I am interested in what, if any, precautions you felt it was necessary for you to take because it certainly looks like you had a great experience.

Larry Tompkins
544WB -6A purchased
building a -7
W52 Battle Ground, WA
Click to expand...

Hi Larry,

Jack Kane, not sure about the spelling is from our neck of the woods, he built a Lycoming engine years ago and had it dynode at http://www.nutterracingengines.com/ down on 4th Plain in Orchards, you might check out that possibility.
 
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