Van's Air Force
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Torque for IO-540 Case Halves?
- Thread starter Phil
- Start date
NO. Too much torque.
See para 7-94 of the overhaul manual. Specifically called out at 75"/lb.
Page 7-17 in my copy. Phil, if you need an electronic copy of the OH manual, send me a PM.
rocketbob
Well Known Member
100 in/lbs was what I was taught when I went to the Lycoming engine school several years back, taught by Lycoming. All still in my notes.
Table 1 in the table of limits section in the OH manual under "bolts, screws, and nuts", lists 1/4" bolts at 96 in/lbs. SSP-1776.
Table 1 in the table of limits section in the OH manual under "bolts, screws, and nuts", lists 1/4" bolts at 96 in/lbs. SSP-1776.
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That table is for bolt torque not specifically called out in the assembly portion of the overhaul manual. Extra torque just weakens the bolts and creates uneven torque on the case halves. More is not better. If Lycoming teaches something other than what is in their printed overhaul manual I can't support that, since the overhaul manual is specifically FAA approved, and that torque number has been the same for the last 40 years.
Unless otherwise specified... Note lubricated threads...
That's the table I used when I reassembled my IO-540V4A5
rvmills
Well Known Member
I just installed new baffles too, and changed those same brackets Phil is talking about. Also had to replace the bracket that holds the spider on (2 more case bolts off, then back on). I was told 75 in-lbs by the local AP/IA as well, but that chart (above) looks like it does call out 96. Figure I'll check with the engine re-builder on the field as well. I know we don't want to overtorque and stretch/weaken the bolts. Just want to be sure...is 75 good and 96 overtorqued, or is 96 good and 75 undertorqued? Is 25 in-lbs significant, over or under? Some respected posters here with differing opinions, so just asking the questions. Is there a ref that calls out 75?
On a related note, I also recently researched the torque call-out for the 1/4-20 nuts that attach my induction adapter elbow to the sump. Saw 40-50 called out in 1 ref, 75 in another and 96 in a third (if I was interpreting correctly). I'll be asking the re-builder that question as well, as 40-50 feels pretty weak, but I don't want to stretch those sump studs! Same size nuts and bolts attach the servo to the front of that elbow, so I'm looking for the appropriate torque for those as well. Thoughts?
Thanks!
Cheers,
Bob
On a related note, I also recently researched the torque call-out for the 1/4-20 nuts that attach my induction adapter elbow to the sump. Saw 40-50 called out in 1 ref, 75 in another and 96 in a third (if I was interpreting correctly). I'll be asking the re-builder that question as well, as 40-50 feels pretty weak, but I don't want to stretch those sump studs! Same size nuts and bolts attach the servo to the front of that elbow, so I'm looking for the appropriate torque for those as well. Thoughts?
Thanks!
Cheers,
Bob
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Yes, when the correct value is 75" lbs, you are applying 33% more torque than called for. That is a lot.
