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Chrysler 6.4L Hemi 392 Engine Review

6.4L Hemi 392 Engine

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.

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. But these two engines don't share neither bore diameter nor stroke size. The new engine has a forged steel crankshaft. The main bearing caps are cross-bolted like in the 5.7 V8. The 6.4L 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 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 each 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 (used in Dodge Challenger, Charger and etc.) have a plastic intake manifold with shorter runners for high-speed, the truck 6.4L Hemi is equipped with an active dual-runner-length intake manifold for low- and mid-range engine speeds without loosing 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 and reliable system completely 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

Manufacturer
Chrysler, Saltillo Engine plant in Ramos Arizpe, Mexico
Production years
2011-present
Cylinder block material
Cast iron
Cylinder head material
Aluminum
Fuel type
Gasoline
Fuel system
Sequential multi-port injection
Configuration
V
Number of cylinders
8
Valves per cylinder
2
Valvetrain layout
OHV
Bore, mm
103.9 mm (4.09 in)
Stroke, mm
94.6 mm (3.72 in)
Displacement, cc
6,407 cc (392 cu in)
Type of internal combustion engine
Four-stroke, naturally aspirated
Compression Ratio
10.9:1 - 6.4L Hemi SRT;
10.0:1 - 6.4L Hemi Ram trucks
Power, hp
366-485 hp (273-362 kW)/4,600-6,000
Torque, lb ft
429-475 ft-lb (582-644 Nm)/4,000-4,800
Engine weight
500 lbs (227 kg) - dry weight
Firing order
1-8-4-3-6-5-7-2
Engine oil weight
SAE 0W-40
Engine oil capacity, liter
6.7 l (7.0 qt) with oil filter
Oil change interval, mile
6,000 (10,000 km)/6 months
Applications
Ram 2500/3500/4500/5500 and Cab Chassis, Dodge Challenger SRT8 / R/T Scat Pack / SRT, Dodge Charger SRT8 / R/T Scat Pack / SRT, Chrysler 300 SRT8 / SRT, Jeep Grand Cherokee SRT8 / SRT, Dodge Durango SRT8 / SRT

6.4L V8 Hemi Engine Problems and Reliability

Like the 5.7 Hemi, the 6.4-liter version is a solid 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 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 thousand 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.

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