How many pistons do I need for my 4.2L Jeep engine?

You will need six pistons for a complete engine rebuild of your 4.2 liter six-cylinder Jeep engine. This part is sold individually.

What does the '.030' on the piston size mean?

The '.030' indicates that the piston is 0.030 inches larger in diameter than the original factory specification. This size is used when the engine cylinders have been bored out to correct for wear or damage.

What is the warranty on this Omix piston?

This Omix piston comes with a limited 5-year warranty from the manufacturer, offering peace of mind for your engine rebuild.

OMIX

Specifications

Brand: OMIX
Part #: 17427.29
UPC: 804314150440

OMIX

Omix Piston 4.2L .030 79-90 Jeep CJ

Name: Omix Piston 4.2L .030 79-90 Jeep CJ
Brand: OMIX
Price: 77.17 USD
Availability: InStock

$77.17

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Omix Piston 4.2L .030 for 79-90 Jeep 4.2L 6-cyl engines. Replaces worn pistons for restored engine performance.

Key Features

Fits 1979-1983 Jeep CJ5, 1979-1986 Jeep CJ7, 1981-1986 Jeep Scrambler, 1987-1990 Jeep Wrangler YJ, 1979-1983 Jeep Cherokee/Wagoneer SJ, 1979-1987 Jeep J-Series Trucks, and 1984-1986 Jeep Grand Wagoneer SJ models with 4.2L engines.
This piston is sized 0.030 inches over the standard bore size.
Sold individually; six pistons are required per engine.
Replaces OE part number 8134441.030.
Covered by a limited 5-year warranty from the manufacturer.

⚠️ CA WARNING: This product can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. Learn more

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Will this fit your vehicle?

Product Details

When you're rebuilding a tired Jeep engine, especially the 4.2 liter six-cylinder, replacing worn internal components is key to getting back that lost power. This Omix piston is a direct replacement for those that have worn down over time, helping to restore your engine's original performance. It's designed to fit a range of Jeep models from 1979 through 1990, including popular choices like the CJ7, Wrangler YJ, and J-Series trucks.

This piston is sized 0.030 inches over the standard bore, which is common when an engine's cylinders have been worn beyond their original specifications and need to be bored out. It's a cast piston, a popular choice for many stock and mild performance applications, offering a good balance of durability and weight. You'll need six of these to complete a full engine rebuild, as they are sold individually.

Remember that installing new pistons is part of a larger engine overhaul. Make sure to consult your service manual for the correct installation procedures and any other related components you might need to replace during your engine build.