Jeep AMC 242 / 4.0L Power Tech I-6 Specs: 3.875 x 3.41 in, 181-190 hp

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Jeep AMC 242 / 4.0L Power Tech I-6 specs: 242 ci (4.0L) 6-cylinder, 3.875 x 3.41 in (98.4 x 86.6 mm) bore and stroke. Rated 181-190 hp, 1997–2006.

The Jeep AMC 242 / 4.0L Power Tech I-6 is oversquare — the 3.8752" bore exceeds the 3.4098" stroke by 13.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.4098" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 40.3 ci (661 cc).

It is one of 14 engines in the AMC Straight-6 family, the smallest at 242 ci. 10 factory variants share these dimensions, rated from 181 to 190 hp across 1997–2006.

Dimensions

Displacement	242 ci / 4 L
Bore	3.8752"
Stroke	3.4098"
Cylinders	6
Configuration	I6
Bore/stroke ratio	1.136

Construction

Block material	cast iron
Head material	cast iron
Valvetrain	OHV
Fuel type	gas
Advertised HP	181–190 hp
Years	1997–2006

What these numbers mean

Bore/stroke character	1.136 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM	3,410 ft/min — conservative for a street engine
Displacement per cylinder	40.3 ci

Run the numbers for this engine

Each link opens the calculator with this engine's specs already filled in.

• Displacement from bore and stroke (calculator)
• Static and dynamic compression ratio calculator
• Piston ring gap for this bore
• Piston speed at any RPM
• Horsepower to torque at any RPM
• What size carburetor (CFM calculator)

Variants sharing these dimensions (10)

These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.

Year	Advertised HP	Code
1997	181 hp	AMC 242 / 4.0L Power Tech I-6
1998	181 hp	AMC 242 / 4.0L Power Tech I-6
1999	181 hp	AMC 242 / 4.0L Power Tech I-6
2000	181 hp	AMC 242 / 4.0L Power Tech I-6
2001	190 hp	AMC 242 / 4.0L Power Tech I-6
2002	190 hp	AMC 242 / 4.0L Power Tech I-6
2003	190 hp	AMC 242 / 4.0L Power Tech I-6
2004	190 hp	AMC 242 / 4.0L Power Tech I-6
2005	190 hp	AMC 242 / 4.0L Power Tech I-6
2006	190 hp	AMC 242 / 4.0L Power Tech I-6

Factory cars with this engine

• Jeep Wrangler: 1997, 181 hp; 1998, 181 hp; 1999, 181 hp; 2000, 181 hp; 2002, 190 hp; 2003, 190 hp; 2004, 190 hp; 2005, 190 hp; 2006, 190 hp

Similar engines

• Jeep 242 — 242 ci
• Jeep 4.0L HO — 242 ci
• Jeep AMC Straight-6 · 3.875" × 3.410" · 9.2:1 — 242 ci
• Jeep AMC 242 — 242 ci
• Jeep AMC 242 (Renix) — 242 ci
• Jeep 40 AMC I6 HO — 242 ci
• Jeep AMC 242 MPI — 242 ci
• Jeep AMC 242 H.O. — 242 ci

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