Overhaul Kit Grade Selection Guide for CAT C6.4 and 3066 Diesel Engines
This article explains the difference between standard (C) and oversized (D, +0.5mm) overhaul kits for CAT C6.4 and 3066 diesel engines. It describes how piston, liner and bearing dimensions vary between the two grades and provides guidance on selecting the correct kit based on cylinder wear measurements. The article covers common applications including CAT 320D and CAT 330D excavators, lists the components included in a typical overhaul kit, and offers practical advice for repair shops and parts buyers to avoid specification errors. Quality grade options and ordering recommendations are also discussed.
Selecting the correct overhaul kit specification is critical for a successful engine rebuild. For CAT C6.4 and 3066 engines, overhaul kits are available in two main grades: standard (C) and oversized (D, +0.5 mm). The key difference lies in the dimensions of pistons, liners and bearings.
Standard (C) kits are designed for engines where cylinder wear remains within factory tolerance. All components are manufactured to original dimensions and can be installed directly to restore engine performance.
Oversized (D, +0.5 mm) kits are used when the cylinder block has been bored or the crankshaft has been ground. Pistons and liners are made to +0.5 mm oversized dimensions to match the reconditioned cylinder bore; bearings need to be selected to the correct undersize for reground crankshaft journals.
Before ordering, measure the cylinder wear:
CAT C6.4 and 3066 overhaul kits typically include:
When ordering an overhaul kit, provide the engine nameplate information or original part numbers. CAT 320D uses the C6.4 engine, while CAT 330D uses the 3066 engine. Confirm the engine model first, then select the C or D grade to avoid mismatched components.
If you need help identifying the correct specification, send a photo of the engine nameplate to our WhatsApp. We will verify and confirm the correct kit for you.
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