Edelbrock Interview: Designing Its New 4.0-Liter Jeep Engine Head

Edelbrock 4.0 Jeep Head-1

The new Edelbrock Performer cylinder head for the 4.0-liter inline six-cylinder engine is designed as a bolt-on performance upgrade, and features all-new better flowing intake and exhaust ports, and a modern combustion chamber design with back cut and swirl polished valves. It retains the stock valve angle, pushrod length and valve cover bolt rail height for use with factory components and off-the-shelf accessories.

Eric Blakely of Edelbrock told us, “We get a lot of requests at the display trailer during the events we attend, and the 4.0-liter Jeep head was one that kept coming up. As much as we wanted to, for a long time we just couldn’t do it because of the size of the casting, and the capabilities of our foundry. We couldn’t do inline sixes, but the supercharger business really changed that.”

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All aluminum construction means that the new Edelbrock head for the 4.0-liter Jeep engine is half the weight of the stock head it replaces.

“Supercharger production pushed our foundry into stepping up there game all-around, in everything from tolerances to sizes to different techniques, and then it became possible for us to built that head. We looked around, and although there are some things out there, we didn’t think there was a really good mass-produced aluminum head out there for this application. You know, if you keep getting enough requests for something, you are going to have to make it.”

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The new Edelbrock head for 4.0-liter Jeep engines offers 1.91-inch intake and 1.50-inch exhaust valves with up to 0.540 inches of maximum lift.

“The challenge that we set for Matt Gamble and our R&D team was that we didn’t think we could justify two different heads, and since we’re well known for our Performer (street legal stock replacement heads) and the RPM (high performance street or strip) product line, we knew this new head had to be able to do both. It had to be emissions legal and have the features for a guy who is building a hardcore rock crawler or race Jeep. That guy is going to boost it or stroke it, and we knew we needed to serve that customer too.”

At the time of this report, the head is pending 50-state emissions legal for 4.0-liter engines when used with factory fuel injection components. It’s also pending 50-state emissions legal for AMC 4.2-liter engines when used with a Mopar Fuel Injection Conversion Kit (E.O. Number D-265-21).

It had to be emissions legal and have the features for a guy who is building a hardcore rock crawler or race Jeep. – Matt Gamble

“I have a bunch of hot rods and motorcycles and I like to go fast and I like horsepower, so when I sit down and design, I want to build the biggest, baddest thing,” Matt Gamble said. “One of the biggest challenges for us was that it had to produce good power, and be practical because it had to be emissions legal.”

“We also wanted it to fit the very broad span of years that the 4.0-liter, and the 4.2-liter before it, were being produced,” remarked Gamble. “This is also a very popular engine, and because of its span of use, there was a lot of data to be collected and assimilated during the design process so that it would fit, bolt-up, and work on that wide spread, something like 20 years, of engines.”

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Larger reinforced rocker bosses provide improved strength at high RPM, and Heli-Coil threaded inserts are used in the manifold bolt holes for added strength.

The new Edelbrock Performer 4.0-liter Jeep head is designed for 1987-2006 Jeep 4.0-liter inline six cylinder engines. It fits the 1991-2006 4.0-liter engine’s intake port locations, but must be used with a 1991-2006 intake manifold. It will also fit 1991-1998 4.0-liter engine exhaust port locations, but must be used with the 1991-1998 factory header or 1991-2006 aftermarket exhaust header. The new Performer 4.0-liter head will also work on 1976-1990 AMC 4.2-liter engines with no modifications to the water jacket, and the appropriate intake manifold and header combination.

Gamble also said, “One of the things our new 4.0-liter Jeep engine head really has going for it is weight savings. It’s about half the weight of the stock head. It also operates at cooler temperatures than stock, and off-road you’re idling or moving slow for long periods of time. The aluminum gets rid of the heat very well. We also spent many hours on the flow bench making sure we got every bit out of the head, while still maintaining the appropriate architecture to work well with all the stock components and offer increased performance capabilities for upgrades such as turbos or superchargers.”

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The new Edelbrock 4.0-liter Jeep engine head features 55 cc combustion chambers, and 144 cc intake and 77 cc exhaust runners.

The new Edelbrock Performer 4.0-liter Jeep engine head features larger reinforced rocker bosses for improved strength at high RPM, and Heli-Coil threaded inserts in the manifold bolt holes for added strength. A 3/4-inch deck throughout the head also provides improved durability, and the head is machined to accept either distributor or coil pack ignition.

“It has big, thick port walls so you can go in there and hog out the ports more if you want. The deck is extra thick too, so you can deck the thing about 30 or 40 to get into some higher compression ranges. You’re going to have to run higher octane fuel, but there’s a lot of power potential there.” Gamble went on to say, “We think it’s going to be really fun to see what the Jeep crowd does with it.”

For more details about the new Edelbrock Performer head for the Jeep 4.0-liter engine, go to the company’s website or call Edelbrock at (310) 781-2222.

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About the author

Stuart Bourdon

A passion for anything automotive (especially off-road vehicles), camping, and photography led to a life exploring the mountains and deserts of the Southwest and Baja, and a career in automotive, outdoor, and RV journalism.
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