ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

Engine Overhaul Tips


Most engine overhaul procedures are fairly standard. In addition to specific parts replacement procedures and specifications for your individual engine, this section is also a guide to acceptable rebuilding procedures. Examples of standard rebuilding practice are given and should be used along with specific details concerning your particular engine.

Competent and accurate machine shop services will ensure maximum performance, reliability and engine life. In most instances, it is more profitable for you to remove, clean and inspect the component, buy the necessary parts and deliver them to a shop for actual machine work.

On the other hand, much of the rebuilding work (crankshaft, block, bearings, piston rods, and other components) is well within the scope of the do-it-yourself mechanic's tools and abilities. You will have to decide for yourself the depth of involvement you desire in an engine repair or rebuild.


The tools required for an engine overhaul or parts replacement will depend on the depth of your involvement. With a few exceptions, they will be the tools found in a mechanic's tool kit (see General Information & Maintenance of this repair guide). More in-depth work will require some or all of the following:

A dial indicator (reading thousandths) and a universal base
Micrometers and telescope gauges
Jaw and screw-type pullers
Valve spring compressor
Ring groove cleaner
Piston ring expander and compressor
Ridge reamer
Cylinder hone or glaze breaker
Engine stand

The use of most of these tools is illustrated in this section. Many can be rented for a one-time use from a local parts jobber or tool supply house specializing in automotive work.

Occasionally, the use of special tools is called for. See the information on Special Tools and the Safety Notice in the front of this guide before substituting another tool.


Procedures and specifications are given in this chapter for inspecting, cleaning and assessing the wear limits of most major components. Other procedures such as Magnaflux® and 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 made 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.


Aluminum has become extremely popular for use in engines, due to its low weight. Observe the following precautions when handling aluminum parts:

Never hot tank aluminum parts (the caustic hot tank solution will eat the aluminum.
Remove all aluminum parts (identification tag, etc.) from engine parts prior to the tanking.
Always coat threads lightly with engine oil or anti-seize compounds before installation, to prevent seizure.
Never over torque bolts or spark plugs especially in aluminum threads.

Stripped threads in any component can be repaired using any of several commercial repair kits (Heli-Coil®, Microdot®, Keenserts®, etc.).

During engine assembly, any parts that will be exposed to frictional contact must be prelubed to provide lubrication at initial start-up. Any product specifically formulated for this purpose can be used, but engine oil is not recommended as a prelube in most cases.

When semi-permanent (locked, but removable) installation is desired, threads should be cleaned and coated with Loctite® or another similar, commercial non-hardening sealant.


See Figures 1, 2, 3, 4 and 5

Several methods are available to repair damaged threads. Heli-Coil® (shown here), Keenserts® and Microdot® are among the most widely used. All involve the same basic principle-drilling out stripped threads, tapping the hole and installing a prewound insert-making welding, plugging and oversize fasteners unnecessary.

Two types of inserts are usually supplied: a standard type for most inch coarse, inch fine, metric course and metric fine thread sizes and a spark lug type to fit most plug port sizes. Consult the tool manufacturer's catalog to determine exact applications. Typical thread repair kits will contain a selection of wound threaded inserts, a tap (corresponding to the outside diameter insert threads) 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 inserts separately in addition to a master kit containing a variety of taps, inserts and installation tools.

Before attempting a repair, remove any snapped, broken or damaged bolts or studs. Penetrating oil can be used to free frozen threads. The offending item can usually be removed with locking pliers or using a screw/stud extractor. After the hole is clear, the thread can be repaired, as shown in the accompanying illustrations and the kit manufacturer's instructions.

Click image to see an enlarged view

Fig. Fig. 1: Damaged bolt hole threads can be replaced with thread repair inserts

Click image to see an enlarged view

Fig. Fig. 2: Standard thread repair insert (left), and spark plug thread insert

Click image to see an enlarged view

Fig. Fig. 3: Drill out the damaged threads with the specified size bit. Be sure to drill completely through the hole or to the bottom of a blind hole

Click image to see an enlarged view

Fig. Fig. 4: Using the kit, tap the hole in order to receive the thread insert. Keep the tap well oiled and back it out frequently to avoid clogging the threads

Click image to see an enlarged view

Fig. Fig. 5: Screw the insert onto the installer tool until the tang engages the slot. Thread the insert into the hole until it is 1/4-1/2 turn below the top surface, then remove the tool and break off the tang using a punch