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When overhauling the engine due to low compression or excessive blowby, new piston rings are installed to bring it back to specification. Normally a re-bore and new pistons are not required -- it is not part of an overhaul. All other parts are inspected and measured (but only replaced if damaged or out-of-specification). To finish the overhaul, new gaskets are installed.
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Overview
If your engine is requiring an overhaul, consider saving time and money by purchasing a good used engine. Often one can be found on trader sites or by asking in the Classifieds. This is also a good time to upgrade to an A14 or A15 engine.
Also see: * Engine Overhaul & Service Data (in Japanese)
- If you are only trying to fix oil leaks, a re-gasketting is called for and an overhaul is not needed
- To check if the engine compression is defective, see Compression Test
- If the engine has a rod knock or main bearing knock it probably needs and overhaul. But you may only need to replace the bearings if the engine is in otherwise good shape.
- If the engine sometimes doesn't run right, don't start with an overhaul but instead troubleshoot it. It may an ignition or carburation issue -- which an overhaul won't fix
Engine overhaul includes:
* New piston rings * New Rod bearings and Main bearings (if required) * New gaskets * Replacement of any out-of-spec parts
Parts that are unlikely to last another 100,000 miles/160,000km are often replaced even if still in working good condition, including the Water pump. Bolt-on Accessories such as Smog Pump and alternator are not part of an engine overhaul.
Not normally part of an overhaul unless out-of-spec or damaged:
* Cylinder Block * Cam bearings * Camshaft * Head milling * Bolts, including Rod bolts and Head Bolts * Carburetor, Distributor or Alternator
Installation
When installing an overhauled engine, it is customary to replace these parts:
- Tune-up#Engine_TUNE-UP including new tune-up parts: Spark Plugs, Distributor Cap, Rotor and Points and new PCV Valve
- Oil and Oil filter change
Overhaul vs Re-manufacture
A re-manufactured engine is a used engine restored to as-new condition. As such, ALL service parts are replaced even if they are working fine or within factory specification.
* Pistons * Piston rings * Bearings ** Main Bearings ** Rod Bearings ** Cam bearings * Camshaft and Lifters * Cylinder Head: ** Valve springs ** Rocker arms * Timing Chain and tensioner * Gasket * Oil pump * Welch Plugs * Acessories including: ** water pump
Non-service Parts
Non-service parts do not require periodic service, last indefinitely, and are not normally replaced unless damaged. They should of course be inspected at overhaul or remanufacture time:
* Pushrods inspected for straightness * Bolts including ** Head Bolts ** Rod Bolts ** Main Bearing Cap bolts