6.4 HEMI Engine 392 – Chrysler, Dodge, RAM, Jeep – Info, Upgrades, Problems, FAQ

Introduced to the market in 2011, the big, bad 6.4L 392 HEMI V8 engine is the next generation of HEMI engines, following the 6.1 HEMI, which has been around since 2005.

The 6.4 is a fresh take on the HEMI design that Chrysler initially used in the passenger line of car models with the 2011 Challenger SRT8 and Charger SRT8 before also being made available as an optional upgrade for the Jeep Grand Cherokee SRT and Dodge Durango SRT.

While the 6.4L was similar to the previous generations of HEMIs, this engine was larger and offered better performance than the smaller 5.7 version, which it replaced. For these and many other reasons, the 6.4 quickly became a favorite among HEMI enthusiasts.

Let’s dive into our handy guide and look at everything you need to know about the 6.4L/392 HEMI engine.

Here is the breakdown of the 6.4 HEMI specs:

Many people think of the HEMI engine as getting its start in the years following WWII. In 1951, Chrysler released their first HEMI car engine, the FirePower engine, as an internal combustion overhead-valve V8 with 180 horsepower.

However, the beginning of the hemi design dates back to 1905, when Belgian carmaker, Pipe, manufactured a 4-cylinder hemi which they used in the Fiat 130 HP Grand Prix race car in 1907.

Regardless of when car enthusiasts want to mark the start of the HEMI, everyone will agree that the early success of the engine led Chrysler to commit to continuing the development of HEMI engines.

Chrysler released the second generation of HEMIs in 1964 with the 426, also called the “Elephant Engine.” The 426 was the first engine to bear the trademark HEMI name, and it was initially designed for NASCAR racing and captured the top three spots in the Daytona 500.

NASCAR eventually banned the 426 in 1965, citing the lack of HEMI street sales and what competitors viewed as an unfair power advantage. The 426, in its original racing version and a de-powered street version, eventually made it to consumers on the market, allowing Chrysler to reintroduce it to NASCAR.

In 2003, Chrysler repositioned the HEMI brand from its original audience of racers and performance car buyers to the mass market of average consumers. The third generation of the HEMI, namely the 5.7L V8 HEMI engine, saw a wide release in many vehicles, including the 2003 Ram 1500, 2500, and 2500.

The updated engine included a redesigned geometry, dual spark plugs, and modern fuel injection technology, all of which significantly improved the HEMI’s performance compared to the previous generation.

The manufacturers updated the 5.7 HEMI engine again in 2009 and used it in even more vehicles, including Chrysler, Dodge, Jeep, and Ram models.

In 2005, Chrysler’s Street and Racing Technology (SRT) Division introduced the 6.1L HEMI. The engine provided an improved 425 hp and 420 lb-ft torque to a new lineup of sportier vehicle models, including the Chrysler 300C, the Dodge Challenger, Charger, and Magnum, and the Jeep Grand Cherokee.

In 2007, the 6.4L 325 Chrysler HEMI engine became available as an individual in-crate purchase. The new design was larger, like the first generations of HEMI engines, and offered 525 hp with 510 lb-ft torque.

The 6.4 HEMI engine was first made available in the 2011 Dodge Challenger SRT but would quickly become an option for the Dodge Charger, Chrysler 300, and the Jeep Grand Cherokee.

While larger and more powerful, the design of the 6.4 HEMI also focused on improving fuel efficiency and enhanced towing force. These improvements made the engine a natural choice for the 2014 Ram Heavy Duty pickup and a wide range of other Ram pickups.

Like its predecessor, the 5.7L, the 6.4L HEMI uses a 90-degree cast-iron piece with a low skirt as the foundation for the engine, but the bore diameter and stroke size are different between the two engines.

The 392 HEMI Charger uses a crankshaft and cross-bolted bearing caps. The 6.4 also utilizes piston cooling jets, which spray oil from the bottom of the pistons to pull away combustion heat. Because of this feature, the 6.4 392 Hemi is built with an oil cooler.

The cylinder heads on the Chrysler 6.4 HEMI utilize two valves and spark plugs on each of the 16 cylinders and oval semi-hemispherical chambers. The heads have a cross-section of head ports with improved intake and exhaust capacity compared to the 5.7. Chrysler manufactures the head covers from plastic material.

This version of the HEMI engine also has a drive-by-wire throttle body. The truck version of the 6.4 uses a dual-length-runner intake manifold and a variable valve timing (VVT) with cam-in-block and a hydraulic cam phasing system.

The truck version of the 6.4 HEMI engine also has Multi-Displacement System (MDS), a cylinder deactivation system that cuts off fuel to four chambers and stops the valve lifters when that extra power is not required.

The 6.4 HEMI has several advantages over the 5.7 or older engine versions. Of course, no engine is perfect, and the 6.4 won’t outperform in every category. Here are a few of the advantages and disadvantages:

Performance

Compared to the 5.7, the 6.4 HEMI horsepower reaches upwards of 100 extra. Because the 6.4 offers a larger 392 cu. in. of displacement, it also provides an additional 60-80 lb-ft of torque over the 5.7 HEMI.

However, when comparing the versions of the two HEMI engines as designers tune them for Ram trucks, the advantage of a 6.4 is less noticeable. This narrower margin is primarily due to the designers tweaking the 6.4 HEMI for Ram trucks to improve fuel economy and towing capacity.

Reliability

The reliability of the 6.4 HEMI is about what you would expect with a slightly above-average rating compared to other engines found in the same types of vehicles or at similar price levels.

That is to say that the 6.4 HEMI, or the 5.7 HEMI for that matter, does not offer the level of reliability that a Honda or Toyota engine is famous for, but it is still dependable.

Read the section below for reliability issues and common 6.4 HEMI problems reported by past owners

Pricing

Pricing constantly fluctuates, so determining how any engine fares in this category is at best a loose guideline that is subject to change. That said, many consider the 6.4 HEMI engine well-priced when factoring in performance, reliability, aftermarket value, etc.

Unfortunately, compared to the 5.7, the 6.4 HEMI is more expensive. The 5.7’s lower price tag is partly due to the simple fact that the 5.7 is an older engine and is easier to obtain if a buyer is willing to hunt down a used one in good condition. The 5.7 also had a higher production, so finding one for parts or replacement engines is much easier than it is with the 6.4 HEMI.

Fuel Economy

Despite the 6.4 being a larger engine than the 5.7, it can sometimes outperform its predecessor thanks to the MDS technology, which many of the 5.7 engines do not have. If a buyer compares a 6.4 MDS-version HEMI to a 5.7 non-MDS HEMI, the 6.4 might have the advantage.

However, despite the MDS technology, the 5.7 345 HEMI will almost always provide better fuel economy than the 6.4 392 HEMI as long as all other factors that affect MPG are comparable.

Towing Capacity

Unsurprisingly, the more significant displacement and better torque of the 6.4L 392 HEMI has the advantage over the 5.7 when it comes to towing capacity. In addition to its increased power, manufacturers have tuned the 6.4 HEMI engine for better towing capacity.

Compared to the 5.7 HEMI engine, the 6.4 has an increased low-end torque of 70 lb-ft more than its predecessor.

The 6.4 392 HEMI is a reliable V8 engine that doesn’t have any severe engine problems. However, there are several issues that can be diagnosed and addressed.

MDS Failure

There have been some reports of solenoid failures in the 6.4’s multi-displacement system (MDS). Fortunately, drivers can manually shut off the MDS technology to allow all eight cylinders to fire until they can make repairs in the event of a solenoid problem.

HEMI Engine Tick

HEMI engines are infamous for an issue nicknamed “Hemi Tick.” This ticking may be nothing more than a peculiarity of the engine that poses no real concerns for reliability or performance.

However, in some cases, an engine tick can indicate a problem, such as faulty lifters or a seized lift roller. These issues, which were also present in the 5.7 HEMI, are most often caused by poor oil flow and can lead to metal-on-metal contact.

A mechanic should examine these issues; otherwise, there is a risk of metal shavings entering the engine oil and more severe problems arising.

Engine Misfires

The 6.4 HEMI can develop a misfire problem. An engine misfire is sometimes a result of issues with a lousy lift roller or solenoid but is most often the result of normal wear and tear. Two of the most common problems that cause misfires are worn-down spark plugs and bad ignition coils.

With 16 spark plugs and eight ignition coils, there are a lot of wear and tear parts that can cause misfires in the 6.4 HEMI.

Here are a few of the most common questions about HEMI engines:

Why is it called a HEMI?

The term “hemi” refers to the hemispherical or dome-shaped design of the cylinders in a HEMI engine.

What makes HEMI engines so powerful?

HEMI engines utilize hemispherical combustion chambers and domed heads (compared to traditional flat heads) to improve the compression ratio. The augmented combustion process means the HEMI offers more power than a conventional engine.

Is a HEMI better than a standard V8 engine?

Because of their hemispherical combustion chambers and domed cylinder, HEMI engines are capable of generating a better compression ratio than the standard V8 engine, which usually has flat cylinder heads.

The reduced surface area on the cylinder heads of a HEMI engine also reduces heat and energy loss compared to a standard V8 engine which also translates to more power and better performance.

What is the expected lifespan of a 6.4 HEMI engine?

If properly maintained and cared for, the 6.4 HEMI should last in excess of 250,000 miles.