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02-28-2011, 07:00 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by jrs14855
I am going to put my faith in Divco on the case dimensions. I do not plan to assemble the case to check dimensions.
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I did that once. Never again, not from Divco or anywhere else. Trust but verify.
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Dan Horton
RV-8 SS
Barrett IO-390
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02-28-2011, 09:26 AM
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Join Date: Oct 2010
Location: Sacramento
Posts: 37
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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.....
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02-28-2011, 07:49 PM
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Join Date: Aug 2006
Posts: 114
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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
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02-28-2011, 09:24 PM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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Quote:
Originally Posted by jrs14855
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.
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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.
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Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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03-01-2011, 12:12 AM
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Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,393
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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.
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03-01-2011, 06:21 AM
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Join Date: Jan 2005
Posts: 1,025
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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."
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03-02-2011, 07:10 PM
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Join Date: Aug 2006
Posts: 114
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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.
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03-07-2011, 07:51 PM
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Join Date: Aug 2006
Posts: 114
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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

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05-26-2011, 07:47 PM
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Join Date: Aug 2006
Posts: 114
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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

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