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crabandy

Well Known Member
I've read the overhaul manual and Service Instruction1029D in regards to torquing the cylinder base nuts. I realize I'm not the sharpest tool in the shed but seems several nuts are left out of the torque sequence. Is it just me?

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Here is one from a Superior Manual. May not be correct for your engine. But, yes, it is not just you.

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So specific yet so vague, especially for the right side of the engine. No mention of the rear nuts of #1 or #3? If I were to do it without service instructions I would tighten the 1/2 inch studs to 300 inch/lbs from the inside out on both sides of the cylinders. Followed by 300 inch/lbs on the 3/8 studs inside to outside. Than finish with 600 inch/lbs on the 1/2 inch studs working from the inside out on the cylinders.
 
Andy,

The portion of the manual you are referencing is only on how to assemble the case halves without the cylinders installed. In the chapter before this section in the Direct Drive overhaul manual has the info on torquing the cylinder base nuts and the sequence.

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Curtis
 
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Curtis,
The overhaul manual sequence is pretty clear , but the Service Instruction 1029D states Part 1 applies to engines which have had all the cylinders removed.

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I guess I'm not exactly sure what your question is. Typically torquing all of the bolts is a two stage process, 1st the crankcase and then 2nd is to torque the cylinders. If you had the engine completely disassembled or just all cylinders removed Part I would be applicable first, then you would do Part II. If you only have removed one cylinder Part II only needs to be accomplished.

This may be more clearly explained in the top paragraph in the second column of the first page od SI1029.
 
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Crankcase

The crankcase thru bolts or captured studs, as the case may be, should be tightened a little at a time. Take care to keep the case halves as even as possible. I use some heavy aluminum plates under the thru studs to better distribute the loads and avoid scoring the area where the cylinders mount.
The way I interpret the manual is that all these thru bolts/studs should be torqued while assembling the case halves. When the cylinders are installed, remove the hardware for that particular cylinder, install the cylinder and re torque.
In my opinion removing the nuts just before installing the cylinder keeps the bearings seated better.
Lycoming only has a sequence for a few of the perimeter bolts. (1/4" bolts around the case perimeter)
 
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