Engine overhaul procedures are fairly standard. In addition to specific parts replacement and specifications for your individual engine, this section is a guide to acceptable rebuilding procedures. Examples of standard practice are shown and should be used along with specific details concerning your particular engine.
In most instances, it is advisable for the do-it-yourself mechanic to remove, clean and inspect the component, buy the necessary parts, and deliver them to a shop for actual machine work. Competent and accurate machine shop services can ensure maximum performance, reliability and engine life.
On the other hand, much of the work (crankshaft, block, bearings, piston rods, and other components) is well within the scope of the do-it-yourself mechanic.
The tools required for an engine overhaul or repair will depend on the depth of your involvement. With few exceptions, they will be the tools mentioned in General Information & Maintenance . More in-depth work will require any or all of the following:
The use of most of these tools is covered in this section. Many can be rented for one-time use from a local parts jobber or tool supply house specializing in automotive work.
Occasionally, the use of special tools is required. See the information on Special Tools and the Safety Notice in the front of this guide before substituting another tool.
Zyglo can be used to locate material flaws and stress cracks. Magnaflux is a magnetic process applicable only to ferrous materials. The Zyglo process coats the material with a fluorescent dye penetrant and can be used on any material. Checking for suspected surface cracks can be more readily done using spot check dye. The dye is sprayed onto the suspected area, wiped off and the area sprayed with a developer. Cracks will show up brightly.
Procedures and specifications are given for inspecting, cleaning and assessing the wear limits of most major components. Other procedures such as Magnaflux
Aluminum has become extremely popular for use in engines, due to its low weight. Observe the following precautions when handling aluminum parts:
Stripped threads in any component can be repaired using any of several commercial repair kits (Heli-Coil, Microdot, Keenserts, etc).
When assembling the engine, parts that will have frictional contact must be prelubed to provide lubrication at initial start-up. Any product specifically formulated for this purpose can be used, but avoid engine oil for this.
When semipermanent (locked, but removable) installation of bolts or nuts is desired, threads should be cleaned and coated with Loctite or other similar, commercial non-hardening sealant.
REPAIRING DAMAGED THREADS
Keenserts and Microdot are among the most widely used. All involve basically the same principle of drilling out stripped threads, tapping the hole and installing a prewound insert, making welding, plugging and oversize fasteners unnecessary.
See Figures 1 through 5
Several methods of repairing damaged threads are available. Heli-Coil
Two types of thread repair inserts are usually supplied: a standard type for most inch coarse, inch fine, metric coarse and metric fine thread sizes and a spark plug type to fit most spark plug port sizes. Consult the part manufacturer's catalog to determine exact applications. Typical thread repair kits will contain a selection of prewound threaded inserts, a tap (corresponding to the outside diameter threads of the insert) and an installation tool. Spark plug inserts usually differ because they require a tap equipped with pilot threads and a combined reamer/tap section. Most manufacturers also supply blister packed thread repair inserts separately, in addition to a master kit containing a variety of taps and inserts, plus installation tools.
Before repairing a threaded hole, remove any snapped, broken or damaged bolts/studs. Penetrating oil can often be used to free frozen threads; the offending item can be removed with locking pliers or with a screw/stud extractor. After the hole is clear, the thread can be repaired as shown in the series of illustrations or in the kit manufacturer's instructions.