Chrysler 6.4L 392 HEMI Engine Specs, Problems & Reliability
6.4L HEMI Info
Chrysler introduced a production version of the crate 392 Hemi engine in the 2011 Dodge Challenger SRT8. It was a 6.4-liter V8 naturally aspirated engine, based on the architecture of the 5.7L Hemi V8. In 2014, a revised version of the 6.4L Hemi SRT became available for the Ram 2500/3500 trucks and Ram 3500, 4500, and 5500 Cab Chassis. The truck 6.4 Hemi engine offers more power and torque than the smaller 5.7L version and is more suitable for hauling and towing like its alternative turbocharged diesel engine option - the 6.7L ISB Cummins. Let's take an in-depth look at the 6.4L/392 Hemi engine design, its common problems, reliability, and longevity.
6.4L HEMI Overview
Like the 5.7 Hemi, the 6.4-liter version is built around a 90-degree, cast-iron cylinder block with a deep-skirt design. However, these two engines don't share neither bore diameter nor stroke size. The new 392 HEMI comes with a forged steel crankshaft. Like in the 345 Hemi, the main bearing caps are cross-bolted. The 6.4 Hemi engine block features piston cooling jets. Oil jets, or squirters, spray engine oil on the bottom of each piston to remove combustion heat. This is one of the reasons why 6.4 Hemi V8s come with an oil-to-water oil cooler. Besides that, the 6.4L V-8 is equipped with revised connecting rods made of higher-strength powder metal material and new, larger-diameter flat-top pistons.
Cylinder heads are similar to the late 5.7 Hemi heads. They have two valves and two spark plugs per cylinder (16 total) and oval-shaped, semi-hemispherical combustion chambers. The 6.4 heads feature a larger cross-sectional area of head ports (11% higher flow in the intake ports and 13% higher flow in the exhaust ports). Head covers are made of plastic. While SRT engines have a plastic intake manifold with shorter runners for high-speed (used in Dodge Challenger, Charger etc.), the truck 6.4L Hemi is equipped with an active dual-runner-length intake manifold for low- and mid-range engine speeds without losing the high-end power of SRT V8s. Both versions come with drive-by-wire throttle bodies. The 6.4L truck engine has a cam-in-block variable valve timing (VVT) which uses a hydraulic cam phasing system developed by Chrysler. Valvetrain features hydraulic roller lifters and sodium-filled exhaust valves.
For efficiency, the truck engine has a cylinder deactivation system called MDS or Multi Displacement System - a simple, reliable system, is fully integrated into the engine's original design. When power is not needed, like on a highway, the system turns off the fuel in four cylinders. It also cuts out the valve lifters for those cylinders in order to eliminate pumping losses. The truck 6.4 Hemi ran on 89 octane gas, but also capable of running on standard 87 octane gasoline.
Engine Specs
Chrysler/Dodge 6.4 Hemi Common Problems and Reliability
Like the 5.7 Hemi, the 6.4-liter 392 Hemi version is a good, reliable V8 engine with even more power and torque. To date, there were no known serious problems with this engine in normal daily-drive usage. Similar to the 5.7-liter version, "Hemi ticking" is found on the 6.4 Hemi V8, as it also has the MDS system. Don't worry, "the family's tick" does not affect anything. The Cylinder Deactivation System (MDS) needs thin 0W-40 and clean oil. Therefore, it is very important to use only the recommended oil and change it on time. In general, the 6.4 Hemi is a big reliable, American pushrod V8 engine with a factory warranty for five years or 100,000 miles.
In stock form, the 6.4 Hemi is a great engine that lasts and serves hundreds of thousands of miles. But, the stock 6.4 is by design not built for boost and pushing more power. The stock bottom end is not good for that. The pistons are not forged and there is not enough meat between the ring lands and the top of the piston. Also, the exhaust manifold may twist from overheat and burst the studs of its fastening. So, it's not like GM's LS series that is more forgiving.