Disassembly

IGNITION SYSTEM

Ignition Harness. Remove the terminals from the top and bottom spark plug. Detach all clips, clamps and grommet plates securing the leads to the engine. The ignition harness on the dual magneto cannot be removed from the magneto without removing the cover from the magneto.
NOTE
Before detaching clamps, clips, grommet plates etc., mark the location of each. Differences in various installations make it impossible for this manual to point out the correct attaching points.
Magneto- Loosen and remove the two 5/16-18 nuts,lockwasher and clamps which hold the magneto to engine. Remove magneto and harness from the engine.


CYLINDERS, PISTONS AND VALVE TRAIN

It is assumed that the ignition harness, intake pipes and primer lines have been previously removed. Intercylinder Baffles. (where applicable) Using the intercylinder baffle tool (64885), release the baffle retaining hook so that it disengages the retainer. Remove the intercylinder baffle and hook from between the cylinders.Oil Drain Tubes. Loosen hose clamps at lower end of tube and slide tube out of hose. Loosen gland nut at cylinder head fitting and remove drain tube.Cylinder. Remove the rocker box cover and gaskets.Rotate the crankshaft to place the piston of no. 1 cylinder at top center of the compression stroke. This will place the valves in closed position and the piston extended away from the crankcase to avoid damage when cylinder is removed. Remove the 5/16-24 self-locking nut from the valve rocker fulcrum . Remove the valve rocker arms and fulcrum from cylinder. Remove the square washers from the stud. Remove the push rods by grasping the end and pulling through the shroud tube. Remove the 1/4-20 plain nut , lockplate and spring . Pull shroud tubes out through the cylinder head and discard the shroud tube seals.
Remove the cylinder base hold-down nuts; then remove the cylinder by pulling straight away from the crankcase. As the cylinder is pulled away, catch and hold the piston to prevent it from falling against the crankcase and being damaged. Discard the cylinder base oil seal rings.Pistons. Remove piston pin plugs from the piston. Using a piston pin puller (64843), pull pin from piston and remove piston.
CAUTION-
After the removal of a cylinder and piston the connecting rod must be supported to prevent damage to the rod and crankcase. This is done by supporting each connecting rod with torque hold down plate ST-222, rubber band (discarded cylinder base on seal rings) looped around the cylinder base studs
Removal of the other cylinders and pistons may be done in any desired order, but less turning of the crankshaft is involved if the cylinders are removed successively in the engine's firing order 1-3-2-4. Left hand rotation firing order 1-4-2-3. Hydraulic Lifters. Remove the hydraulic lifter from the crankcase. Place each lifter as removed from crankcase in its proper location in the cleaning basket. The hydraulic lifters must be replaced in the same location in crankcase from which they were removed.
Cylinders- Place cylinder over the cylinder holding block (64526-2), assemble valve spring compressor (ST-419) on cylinder, and compress valve springs far enough to remove the valve retaining keys.
NOTE-
If keys are stuck tight in spring seat, a light blow with a leather mallet on top of compressor will release keys. Remove all valve spring seats and springs from rocker box, keeping parts for each valve separate. Hold valves by the stem to keep them from dropping out of the cylinder, and remove cylinder from holding block. Now reach inside of cylinder and remove valves. If difficulty is experienced in pulling the tops of the valve stems through the valve guides, push the valves back in position and clean the carbon from the stems.





OIL SUMP AND FUEL INDUCTION

Intake Pipes.
Loosen and remove the capscrews that attach the intake pipe flange to the cylinder head intake port. Loosen the hose clamps and slide the pipe off the sump connector. Mark the intake pipes as they are removed from the engine so that they may be reassembled in the same location.

Carburetor.
Remove the carburetor from the mounting pad of the sump.
Oil Suction Screen.
Unscrew the hex head plug and remove gasket and suction screen.
Oil Sump.
Remove the fastenings from the periphery of the sump and remove the sump.



CRANKCASE, CRANKSHAFT & RECIPROCATING PARTS

Remove the oil pump and vacuum pump body assembly by removing the four plain nuts, lockwashers
and plain washers. Discard the "o" rings seal and oil seal in pump body. Remove the driven impeller from the crankcase and the driving impeller from the pump shaft.
The oil pump shaft cannot be removed until the crankcase is parted.Remove the oil pressure screen housing and the oil cooler adapter or the oil filter adapter assembly (where applicable) from crankcase. Remove the oil cooler adapter from the oil filter adapter. Remove the oil filter and adapter plate. Also remove thermostatic oil by-pass valve. Discard all gaskets.
Remove the oil relief valve plug, gasket, spring and ball from the crankcase.
Remove the oil filler tube.
Remove the nuts and bolts from the parting surface of the crankcase, which hold the crankcase halves together.
Remove the crankcase from the overhauls stand and place on the work bench.
Remove the starter ring gear support assembly from the crankshaft propeller flange by tapping lightly on the rear of the assembly. The alternator drive belt will be removed with this unit.
Remove the external retaining ring , seal retainer and "o" ring seal from the tachometer drive
adapter. The tachometer drive adapter can not be removed until the crankcase is separated.
On engines equipped with a governor drive, remove the governor drive cover, "o" ring, and governor
drive thrust washer, from the nose of the crankcase.

The crankcase may be separated by first resting on the bottom of crankcase and gently tapping with a soft hammer the thru-studs on the loose ends until the crankcase begins to separate. Place the crankcase on the left side and continue to remove the right half of crankcase. Reach down through the cylinder pads and push the crankshaft bearing insert down on the crankshaft, so they will not fall when crankcase half is removed. Separate the crankcase by hand and remove the bearing inserts and crankshaft assembly.
Remove the camshaft, tachometer drive adapter and the crankcase breather baffle. Engines equipped with a propeller governor it is necessary to remove the governor drive gear at the time the camshaft is removed. Also remove the governor drive shaftgear from the right half of the crankcase.



Camshaft.
Remove the camshaft gear and the tachometer shaft.
Remove the oil and vacuum pump drive shaft by removing the nut and lockplate. Use service tool ST-416 to turn pump shaft while holding nut with open end wrench. Remove oil pump drive gear. Remove drive shaft from crankcase.
Crankshaft.
With the crankshaft properly supported at front and rear main bearings, remove the nuts securing the rod caps to the connecting rod.
Remove the rods by tapping on the rod bolts with a soft hammer. Discard the bearing inserts, bolts and nuts. Reassemble each cap with its corresponding rod. Rods and caps are not interchangeable.
Remove the crankshaft oil seal and the expansion plug from the crankshaft. Do not remove the propeller flange bushings from the flange of the crankshaft unless they are damaged and/or loose.







Counterweights.
Counterweights are disassembled from the crankshaft merely by removing the retaining rings, after which the washers ,rollers and counterweights may be removed from the crankshaft ear.
To remove the crankshaft gear flatten out the lockplate and remove the hex head screw or screws
Tap the crankshaft gear gently with a fibre drift to remove gear from crankshaft. Do not remove the dowel from rear of crankshaft ““less it has been obviously damaged.

Shop safety and preparation for overhaul

Once the gasoline and oil is drained, all overhaul work can be done indoors. Without gas, there is little risk and working indoors is generally much more convenient. Therefore, you need to decide where to set up for the overhaul. The best location will be relatively dust free, well lit, and not likely to be required for other purposes. Your engine may be remaining in a disassembled state for some time if you need to obtain replacement parts. Also, even with its bodily fluids removed, an old engine will stink.

Tools and equipment

An engine overhaul does require some special tools. These tools are used for measuring clearances as well as special assembly or disassembly procedures unique to the engine.
Here's a list of tools that you might need. The list will vary for different types of engines, and this list is for the Continental O-470. For tools that are unique to the engine, you should consult the engine overhaul manual. Note that the overhaul manual will often list many special and highly expensive tools that the factory uses but that you don't need to complete an overhaul.
If you're working with a mechanic, chances are the mechanic already has these tools and through negotiation you can use your mechanic's tools. Make sure you respect your mechanic's tools.
As somebody who does a lot of maintenance, I have a policy that whenever I need to use one of my mechanic's tools then I buy one for myself. This isn't always practical, but works well for most tools.
Hand Tools
General hand tools: You'll need the following (all in fractional inch sizes - no metric). I recommend the high-quality full polish Craftsman or Snap-On tools.
• Short-pattern "stubby" box-end wrench set, 1/4" to 3/4"
• Long-pattern box-end wrench set, up to 1" size
• 60 degree double-offset box-end short-pattern wrench set (Snap-On makes an excellent set, and they're sometimes necessary for tight fits).
• X-Acto knife, angle blades and flat blades for gasket scraping.
• Cotter key puller tool
• Duckbill and needlenose pliers
• Small set of snips
• Crescent F-wrench with 2" capacity
• 1/4" drive 12 pt shallow socket set and drivers, with extension set
• 3/8" drive 12 pt shallow socket set and drivers, with extension set
• Assorted screwdrivers
• Allen key set
• Brass hammer
• Soft mallet
• Cleaning brushes
• Drifts of various sizes to help with assembly
You might also find yourself in need of deep sockets and/or universal drive sockets, depending on the engine.
You must have a good, calibrated, torque wrench for any overhaul. I prefer the "clicker" type of torque wrench where you pre-set a torque value and then turn until the wrench "clicks" off at that specified value. The clicker types are more expensive than the beam type wrenches where you read the torque off of a scale attached to the wrench. Both work equally well assuming the wrench has been calibrated.
You'll typically want a small and a large wrench for convenience. A small wrench is best for the smaller jobs and tight clearances, and it is lighter. A large wrench is handy for leverage when doing the larger torque values like through-studs. Your wrenches should have a range of about 50 inch-lbs up to about 800 inch-lbs.
Specialty Tools
There are a number of specialty tools that are required for any given aviation engine. Many of these tools have use in regular maintenance outside of overhauls, so they're handy to have around all the time.
I recommend these suppliers:
• Aircraft Tool Supply
• US Tool
• Sacramento Sky Ranch
• Aircraft Spruce
Aviation spark plug socket. You need a special socket for aviation plugs. Make sure you have adapters for your torque wrench's drive size.
Cylinder base wrench set. These wrenches are strangely bent to allow you to get to the cylinder base nuts when the cylinders are installed on the engine. There are different sizes required for different engines so make sure you check sizes.


Piston Ring Compressor. I recommend the wrinkle-band type. Make sure you get one large enough for your engine. Many automotive compressors are not large enough for aircraft pistons.

Timing disk and propeller dome adapter, and magneto timing box. To set timing on the engine after reassembly.

Pushrod Tube Spring Compressor. Necessary when installing Continental engine pushrod housings.
Valve spring compressor. If you're doing top end work, you should get this specialty compressor tool.

Bearing puller. Might be necessary for disassembling accessory drives.
Engine crane. Get a portable hydraulic shop crane from your local auto parts store. Usually these come in a 2 ton capacity and can often by found with folding legs to make storage easier.
Engine stand. Check Trade-A-Plane for engine stand ads. Do not attempt an overhaul without a stand. You should also get the rolling casters so that you can move the engine around during the overhaul.

Safety wire twister pliers. I recommend getting a good set of twisters, not a cheapo import. Robinson and Milbar are the best. I particularly recommend the Milbar Tigerwave 6" and 9" twisters.

Measuring tools. You're generally going to need:

Outside Micrometers. A good mix is 0-1" and 1-2" fixed, and a 0-6" interchangable anvil set
Snap-gauges, buy a set up to about 6 inches.
Bore gauge, up to 6".

Caliper

I prefer direct digital-reading equipment to minimize confusion, but that costs more than the old style analog gauges and both work equally well. Mitutoyu Digimatic or Starrett are good brands. McMaster-Carr is a good supplier.

Documentation
You will absolutely need a copy of the engine overhaul manual and the parts manual. The best source for these is the factory.
You should also have a copy of the latest service bulletins for the engine, also available from the factory.
While you are removing your engine and disassembling it, make sure you document the existing installation. I recommend a decent digital camera for convenience. Having the photos provides for a record both during reassembly and useful documentation of the engine's previous condition and its overhauled state that you should include with the engine records.

Supplies
Get a bunch of plastic ziplock bags and 3x5 index cards to bag and tag parts as you remove them. I buy the sandwich size and the 1 gallon freezer-bag size.
Aero grade Hylomar. Gasket and parting seam sealant. Great stuff.
Safety wire. You'll need 0.020, 0.032, and 0.041" stainless steel safety wire.
Fuellube. An all-purpose lubricant useful when assembling fittings.
Parker O-Lube. For lubricating O-rings during assembly.
Assembly lube. I use Hyper-Lube Assembly Lube right out of the bottle (available at auto parts stores). You can also use fresh 50 weight oil.
Specialty lubes. Certain parts may require specialty lubes during assembly. Consult your overhaul manual.
Silicon Baffle seal material. You'll need several feet of baffle seat material. I recommend the silicon fiber-reinforced variety. You'll probably also need attachment rivets and backing washers.
Miscellaneous Hardware. You should decide whether you're going to replace small hardware items such as screws, nuts, washers, and bolts. If so, you will need to get replacements.
Engine paint. I recommend Randolph engine enamels. Make sure you also buy some solvent/reducer for spray dilution and cleanup. If you're looking for a brighter, non-stock engine color (e.g. red or blue to match your airplane) then I recommend Bill Hirsch engine paint, which is good stuff but doesn't come in "aircraft" colors. The Hirsch paints thin with Xylene.
Wicks or Aircraft Spruce are good suppliers for the miscellaneous stuff.

Installation and Test Run
You'll need a pre-oiling rig to pre-oil the engine before it is run for the first time. This can be as simple as a pressure tank with two taps and valves. You fill the tank with oil, attach an outflow hose to one tap and connect the hose to the engine. You connect compressed air to the other tap to pressurize the tank and force the oil into the engine oil galleries and bearings.

overhaul shop

These works are carried out in an overhaul shop
 . Receiving inspections
 . Disassembly & cleaning
 . Overhaul inspection
 . Assembly
 . Engine Test

What is a over haul and why engine overhaul is necessary ?

a complete engine overhaul involves replacing piston rings, reboring or honning cylinder walls, replacing pistons (if the cylinders are rebored), replacing main and connecting rod bearings, regriding the crankshaft to restore the journals (if needed), and restoring the valves. Rebuilding parts like the starter, distributor, carburetor and alternator while the engine is being overhauled is common to ensure that the entire runs like new but isn't always necessary.

When overhauling an engine, there are four basic choices for the kind of overhaul you want:

Choice 1: Factory Remanufactured Engine. This strictly speaking isn't an overhaul, as it results in a zero-timed engine. You send your run out engine "core" to the factory, either Continental or Lycoming, and you get back an engine that is built to new engine standards. Some parts are re-used such as crankshafts and cases, but the top end parts are generally replaced with new parts. Since the factory does the work, they can certify the engine as "zero time" and it counts as a brand new engine as far as the logbook times are concerned.

Choice 2: Factory Overhauled Engine. The factory overhauls the engine, but the engine is not zero timed. In theory a modern factory overhaul, where the factories have begun using more new parts, will result in exactly the same engine as a reman.

Choice 3: "Name Brand" Overhaul Shop. There are a number of "name brand" overhaul shops that have enough volume to justify national advertising for their services. These shops are specialists in engine overhauls and should be the best experts you can find outside of the factory

Choice 4: Field Overhaul. Any certified Powerplant mechanic with Inspection Authority can perform and sign off an engine overhaul. The mechanic may or may not be associated with a FBO, although most are. A field overhaul is often performed locally and so you have the most knowledge of the mechanic, and potentially the most control over the schedule and overhaul options ranging from a completely vanilla service-limits overhaul up to a completely tricked out custom built and finished engine. It is also potentially the most work for you as owner and is probably the least valued by the marketplace for resale value because buyers of your aircraft usually will not have the same knowledge of and trust in your mechanic that you do.A field overhauler will almost never have direct access to specialized overhaul tooling and equipment such as cylinder boring and honing machines or valve seat grinders.

In practice this is not an issue because with there are specialty parts overhauler shops that make a business ofdoing this kind of work and your mechanic will simply send the parts out.The advantages of a field overhaul are price and flexibility