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Thread: Torque Values for intake and exhaust nuts...bolts ???

  1. #1

    Default Torque Values for intake and exhaust nuts...bolts ???

    I am having a hard time finding the correct torque values for my o320 exhaust nuts, and intake flange bolts. Where should I find these values. Don't see them in overhaul manual, or TCDSLYCOMING for the engine,

  2. #2

    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    Same question for an A65 Continental. I'm particularly interested in the appropriate torque for the brass exhaust nuts.

  3. #3
    Pacerfgoe's Avatar
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    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    When I did my engine, I just used the "standard torque values" listed in table 1. It says to use these values unless otherwise listed. This table is in the back of the Lycoming overhaul manual.

  4. #4

    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    Thanks

    That was what we used. 8 ft lbs for 1/4 inch nuts or bolts, and 17 ft lbs for 5/16 .

    Thanks

  5. #5

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    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    I can't believe nobody has stepped in here. The torque values you seek are in Section V of the Lycoming Direct Drive Overhaul Manual (P.N 60294-7 in Service Table Of Limits Part 1 Section V). 5/16-18 exhaust port studs are specifically listed as Item No 906 (852 in the "old" Ovhl Manuals) and are FORTY INCH-POUNDS MINIMUM. That's "THREE POINT THREE THREE THREE foot-pounds". ALL THE TIME when removing exhaust manifold nuts I find where the studs back out instead of the nuts coming off because people use EXCESSIVE torque. Lookit, that area gets HOT, and things get bigger when they are hot...then they cool, everything shrinks and the gaskets leak. Expanded Inconel pipe flanges have all the "breaking power" that water hyas when it expands when frozen!!! That's enough power to split boulders and MOUNTAINS. Forty in-lbs sounds ridiculously "loose"...but Lycoming knows what they are doing. When the engine is stabilized at operating temp, by golly, these little studs with 5/16 nuts on them are WAY over torqued at "standard" torque values. Could THAT be why there is a Special Torque Value Section in the Manual??? ALL the torques you need are right there in the same "book". There is VERY LITTLE on a light enough to fly aircraft engine that isn't "highly loaded", and THOSE ITEMS you will use Standard Torque for. Sorry if sometimes they might be a nuisance to dig out, but hey...if everybody could do it, everybody WOULD. Them's that "can't" should apply themselves a little more, or let somebody "serious" do it for them (I know how that sounds, but it's just simple truth. Sorry for sounding gruff).

    I don't mean to sound snotty but all the info is in the proper TechPubs you need to have and use for this stuff (or you should not be attempting it).

    The brass exhaust nuts on the A and C Series Continentals cannot be tightened to standard torques because you will strip them. Over tightening those will result is "loose" exhaust nuts after only a couple of heat/cool cycles. Using a Snap-On flex drive socket and a short 1/4" ratchet, you tighten those
    "as tight as you can get them with that little wrench" and you don't use a Cheater Pipe, and you don't strain your wrist. Same deal...when they get hot, the flange "grows" and they get plenty tight. If your flanges don't meet squarely on the port faces, you will NEVER stop blowing gaskets until the flanges fit squarely no matter HOW tight you force them with brass nuts. "Double gaskets" is NOT the answer (although it does work in some cases, but when the job is done correctly the first time, you will not blow gaskets repeatedly, you will not shear nuts and you will not "back out" or shear of the studs.
    Last edited by JohnW; 02-20-2012 at 07:40 AM.

  6. #6

    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    Thanks very much. Will locate ASAP.

  7. #7
    pa20's Avatar
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    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    I am going to go out on a limb here, but I believe all this discussion is not answering the original poster's question. The Textron Lycoming manual spec quoted above specifies a minimum 40 lb/in torque for driving the the STUD, and is not referring to the nut. Specifying a MINIMUM torque value assures that the stud has sufficient interference, and that an oversize stud is not required.
    There is no reference that I can find in the Lycoming O/H manual that references the torque of the exhaust nut. A brief search on the web gleaned some varying specs from 90 lb/in (Enstrom SB for exhaust repair) to a 160-180 lb/in value (attributed to Lyc. and SWPC) in an individuals blog*. http://home.earthlink.net/~andy2220/...siontables.pdf
    Having a minimum value on a installation of the exhaust nut just did not pass the "sniff test", especially as it specifically refers to the stud.

    My research indicates that the intake pipe flange bolts (1/4-20) should be torqued to 96 lb/in.

    * I noticed this morning that the link posted above is part of Andy's website, which is a great source of information in case just as this. There is so much information on our SWP's that is just not available in the mfr's publications, but if you have a look at his data you are likely to find the correct information.
    Last edited by pa20; 02-23-2012 at 09:25 AM.
    Mark Ohlau
    PA-20 N7744K Proud Member - 2014 Donation Paid

  8. #8
    Pacerfgoe's Avatar
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    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    I think I have to agree with Mark on this one. The reference in the manual says "exhaust port studs" and if you find reference 906 in the illustrations it clearly points to the stud. If the nuts were to have a torque less or more than standard, it would be listed in the tables.

  9. #9

    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    Spoke with Don Freeman of Aircraft Engines inc. today, he said the min 40 inch lb torque is for the STUDS. Std values of 96 in lb for 1/4" or 204 in lb for 5/16 nuts or bolts should be used for intake and exhaust flange torques. The item referenced in previous replies. Item 906 does specifically state " STUD".

    Any further thoughts or inputs. Appreciated all the replies..

    Mark S.

  10. #10
    pa20's Avatar
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    Default Re: Torque Values for intake and exhaust nuts...bolts ???

    Looks like we got the correct info out there for our members. Thanks guys. The reality of having planes flying with exhaust nuts that are not sufficiently torqued is too horrendous to contemplate!
    Mark Ohlau
    PA-20 N7744K Proud Member - 2014 Donation Paid

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