Inactivity

            Both manufacturers agree that inactivity in excess of 30 days strongly suggests the need for some special preservation methods and chemicals, especially if the aircraft is located near salt water or similar humid environment.
Lycoming's procedure is as follows:
Install a preservative by one of the following methods:
        Drain the lubricating oil from the sump or system and replace with a preservative oil mixture. This preservation mixture consists of one part by volume MIL-C-6529C Type I concentrated preservative compound added to three parts by volume of MIL-L-6082C (SAE J1966), Grade 1100, mineral aircraft engine oil or oil conforming to MIL-C-6529C Type II. Follow carefully the manufacturer's instructions before use.
       An alternative method is the use of Cortec VC1-326 preservative concentrate added to the original oil at a ratio of 1 part VC1-326 to 10 parts of oil.
      Operate the engine until normal temperatures are obtained. Do not stop engine until oil temperature has reached 180°F. If weather conditions are below freezing, oil temperature should reach at least 165°F before shut down.
      Remove sufficient cowling to gain access to the top spark plugs and remove them.
Through the spark plug hole, spray the interior of each cylinder with approximately two ounces of the pre-servative oil mixture using an airless spray gun (Spraying Systems Co., Gunjet Model 24A-8395 or equivalent). In the event an airless spray gun is not available, a moisture trap may be installed in the air line of a conventional spray gun.
        Reinstall spark plugs and do not turn crankshaft after cylinders have been sprayed. Note: Oils of the type mentioned are to be used in Lycoming aircraft engines for preservation only and not for lubrication. See the latest revision of Textron Lycoming Service Instruction No. 1014 for recommended lubricating oil choices.
       If the aircraft is stored in a region of high humidity, or near a seacoast, it is better to use dehydrator plugs instead of merely replacing the spark plugs as directed in the preceding step. Cylinder dehydrator plugs, MS-27215-2 or equivalent may be used.
       Preferably before the engine has cooled, install small bags of desiccant in exhaust and intake ports and seal with moisture impervious material and pressure sensitive tape. Any other opening from the engine to the atmosphere, such as the breather, and any pad from which an accessory is removed, should likewise be sealed. (Desiccant may be obtained through a             Textron Lycoming distributor, or aviation catalog or Internet in different quantities.)
       Firmly attach red cloth streamers to any desiccant bags installed in the intake and exhaust passages to insure material is removed when the engine is made ready for flight. Streamers should be visible from outside the aircraft. The propeller should be tagged, "Engine preserved—do not turn the propeller."
         At 15-day maximum intervals, a periodic check should be made of the cylinder dehydrator plugs and desic-cant. When the color of the desiccant has turned from blue to pink the preservation procedure must be repeated.
       To return the aircraft to service, remove seals, tape, and desiccant bags. Use a solvent to remove tape residue. Remove spark plugs or dehydrator plugs.
         With the magnetos off rotate the propeller by hand through sufficient rotation to remove excess preservative oil from the cylinders. Drain the remaining preservative from the engine through the sump.

Source for preservative oil:

De-Preservation

                          It is important to remember that long-term preservation of engines can result in trapping large amounts of oil in the combustion chambers of one or more cylinders. For this reason, engines should not be rotated until all of the preservative oil is drained away. Failure to do so can result in damage to the piston, connecting rod, and crankshaft of the flooded cylinder.
                     To return the aircraft to service, remove seals, tape, and desiccant bags. Use a solvent to remove tape residue. Remove spark plugs or dehydrator plugs.
            With the magnetos off, rotate the propeller by hand through sufficient rotations to remove excess preservative oil from the cylinders. Drain the remaining preservative through the sump.
Most engines are equipped with a quick-drain oil fitting on one side of the oil sump and a standard AN plug on the other. Remove both in order to drain as much of the preservative oil from the sump as possible. Uninstalled engines should be hoisted level, then tilted as required to aid in draining of the oil.
             If the spark plugs were installed in the flooded cylinders, all traces of oil should be removed from the firing end and the external barrel with clean solvent or MEK prior to reinstallation. Remove all dehydrator bags, tape, plugs, and barrier paper from the induction system, exhaust ports, breather lines, and so on. Drain and flush the carburetor or other fuel components with fuel, and re-safety all drain and vent plugs as necessary. Check all fuel and oil hoses and intake ducts for security and leaks.
             After servicing the oil sump with the proper grade of oil, wash and pre-flight the engine and engine compart-ment, perform a ground run to operating temperature, and check for leaks. If all is satisfactory, install the cowling and make a logbook entry noting the reversal of the preservation process.
            Keep the first flight local to be sure there were no items missed or loose items. Double check for any pest dam-age or roosting, as well as hand operate all control surfaces to feel for any signs of binding or corrosion in hinges.
              That includes a visual check and light thumping on the tail and control surfaces, as well as the gear wells and en-gine compartment to assure there are no stubborn tenants or nest residues. If there is any signs of varmints or in-sect activity, more serious investigation is called for such as panel removal and the use of a borescope. If you plan on not doing all these things for storage, at least consider doing some of them such as the dehydrator plugs and desiccants as well as the use of vapor corrosion inhibitors) VCI technology for the cabin and avionics.

Engine Mount

Fuel system

Pulling the Prop by hand

     Reference to Lycoming SL 180B: "Pulling engines through by hand when the aircraft is not run or flown for a week or so is not recommended. Pulling the engine through by hand prior to start or to minimize rust and corrosion does more harm than good. The cylinder walls, piston, rings, cam and cam followers only receive splash and vapor lubrication. When the prop is pulled through by hand, the rings wipe oil from cylinder walls."

            The cam load created by the valve train wipes oil off the cam and followers. After two or three times of pulling the engine through by hand without engine starts, the cylinders, cam and followers are left without a proper oil film. Starting engines without proper lubrication can cause scuffing and scoring of parts resulting in excessive wear."

       Note that pulling the prop through prior to starting is a different story. Here you will be starting the engine and it will be immediately receiving lubrication. Also, pulling the prop through in this situation will check for the condition of the valves i.e. you are feeling for any flat spots in the compression, or other untoward signs of abnormal prop feel as the pistons are cycled.