This Edelbrock Performer Aluminum Cylinder Head is a high-quality performance upgrade for AMC / Jeep 4.2L and 4.0L inline-six engines. For Full Size Jeep owners, this is most commonly used with AMC 4.2L / 258 inline-six applications..

The Performer cylinder head is designed to improve airflow, combustion efficiency, and durability compared to a factory cast-iron head. It features improved intake and exhaust port design, a modern combustion chamber, back-cut valves, and swirl-polished valves to help move air through the engine more efficiently. The aluminum construction also provides a major weight savings compared to a stock cast-iron head.

This head retains the stock valve angle, pushrod length, and valve cover bolt pattern, allowing it to work with many factory-style components and common aftermarket accessories. Larger reinforced rocker bosses improve strength at higher RPM, while Heli-Coil threaded inserts in the intake manifold bolt holes add durability. The 3/4" deck thickness throughout the head also helps improve stiffness and long-term reliability.

This cylinder head comes fully assembled and is designed for use with a flat tappet camshaft. It is designed, cast, machined, and assembled in the USA.

Important Compatibility Notes

This head is designed with 1991–2006 4.0L intake port locations and 1991–1998 4.0L exhaust port sizing.

Because of that, it must be used with a 1991–2006 4.0L-style intake manifold and a 1991–1998 4.0L-style exhaust manifold or compatible aftermarket header. Aftermarket headers may also be used, but compatibility should be verified with the header manufacturer.

This head is not compatible with 1999–2006 factory OEM exhaust manifolds. If used in place of a 1999–2006 exhaust setup, a compatible aftermarket header is required.

For Full Size Jeep 4.2L / 258 applications, this should be treated as a performance upgrade, not a simple stock replacement for every original 258 intake and exhaust setup.

Features

• Performer aluminum cylinder head upgrade
• Designed for AMC / Jeep 4.2L and 4.0L inline-six engines
• Fully assembled
• Improved intake and exhaust port flow
• Modern combustion chamber design
• Back-cut and swirl-polished valves
• Reinforced rocker bosses
• Heli-Coil threaded intake manifold bolt inserts
• Retains stock valve angle, pushrod length, and valve cover bolt pattern
• Machined for stock or aftermarket distributor and coil-pack ignition setups
• Designed for flat tappet camshaft use
• Made in the USA

Additional Notes

Recommended spark plug is Champion RC12YC or equivalent, using a 14mm x 3/4" reach plug with flat gasket seat.

Recommended 4.0L-style head gasket options include Edelbrock #7348.

Guide plates are not included. If using roller rockers, a valve cover spacer may be required for proper clearance.

Dyno results and horsepower gains will vary depending on block, crankshaft, camshaft, compression, intake, exhaust, fuel system, ignition, and tuning.

This Part Fits:

• All with 4.2L 258 AMC 6-Cylinder Engine

Specifications

• Series: Performer
• Material: Aluminum
• Quantity: Sold Individually
• Camshaft Type: Flat Tappet
• Horsepower Range: 200–300 HP
• Combustion Chamber Volume: 55 cc
• Deck Height: 9.435"
• Deck Thickness: 0.750"
• Intake Valve Diameter: 1.91"
• Exhaust Valve Diameter: 1.50"
• Intake Runner Volume: 144 cc
• Pushrod Diameter: 0.312"
• Valve Angle: 10°
• Valve Spring Diameter: 1.26"
• Valve Spring Maximum Lift: 0.540"
• Valve Stem Diameter: 0.3125"
• Seat Angle: 45° intake / 45° exhaust

Emissions Notes

This cylinder head is 50-state emissions legal for 4.0L engines when used with factory fuel injection calibration and components under E.O. Number D-215-94.

For 4.2L engines, emissions legality may depend on the fuel injection conversion and applicable emissions approval. Verify local requirements before installation on emissions-controlled vehicles.

Installation Instructions