A factory version of the crate 392 Hemi engine was used in the 2011 Dodge Challenger SRT8. It was a 6.4-liter naturally aspirated V8 engine based on the 5.7-liter Hemi V8 design. In 2014, a new 6.4L Hemi SRT engine was launched for Ram 2500/3500 pickup trucks, as well as Ram 3500, 4500, and 5500 Cab Chassis.
The 6.4-liter Hemi engine in the truck delivers more power and torque than the 5.7-liter version, making it more suited for hauling and towing than the 6.7-liter ISB Cummins turbocharged diesel engine.
Let's take a closer look at the 6.4L/392 Hemi engine, including common faults, reliability, and lifespan.
The 6.4-liter Hemi, like the 5.7 Hemi, is built on a 90-degree cast-iron cylinder block with a deep-skirt design. The bore diameter and stroke size of these two engines, however, are not the same. The new 392 HEMI comes equipped with a forged steel crankshaft. Like the 345 Hemi, the main bearing caps are cross-bolted.
The 6.4 Hemi engine block has piston cooling jets. Oil jets, also known as squirters, spray engine oil on the bottom of each piston to minimise combustion heat. This is one of the reasons why 6.4 Hemi V8s have an oil-to-water oil cooler. Aside from that, the 6.4L V-8 boasts new, larger-diameter flat-top pistons and new, higher-strength powder metal alloy connecting rods.
The cylinder heads are similar to those used on late 5.7 Hemi engines. There are two valves and two spark plugs in each cylinder, totaling 16 valves and spark plugs, as well as oval-shaped, semi-hemispherical combustion chambers.
The 6.4 heads' head ports have a larger cross-sectional area (11 percent higher flow in the intake ports and 13 percent higher flow in the exhaust ports). The head covers are made of plastic. While SRT engines use a plastic intake manifold with shorter runners for high-speed performance (as seen in the Dodge Challenger and Charger), the truck's 6.4L Hemi has an active dual-runner-length intake manifold for low- and mid-range engine speeds without losing the SRT V8s' high-end power.
Both versions come fitted with drive-by-wire throttle bodies. The 6.4L truck engine has a cam-in-block variable valve timing (VVT) system with a hydraulic cam phasing mechanism designed by Chrysler. In the valvetrain, hydraulic roller lifters and sodium-filled exhaust valves are employed.
The truck engine has MDS (Multi Displacement System) cylinder deactivation technology, which is a simple, reliable system that is totally integrated into the engine's original design for enhanced efficiency. While power isn't needed, such as when driving along the highway, the system turns off four cylinders.
By eliminating the valve lifters for specific cylinders, it also reduces pumping losses. The 6.4 Hemi truck required 89 octane gasoline, although it could also run on standard 87 octane.
Manufacturer: Chrysler, Saltillo Engine plant in Ramos Arizpe, Mexico
Production years: 2011-present
Cylinder block material: Cast iron
Cylinder head material: Aluminium
Fuel type: Gasoline
Fuel system: Sequential multi-port injection
Number of cylinders: 8
Valves per cylinder: 2
Valvetrain layout: OHV
Bore: 103.9 mm (4.09 in)
Stroke: 94.6 mm (3.72 in)
Displacement: 6,407 cc (392 cu in)
Type: Four-stroke, naturally aspirated
Compression Ratio: 10.9:1 - 6.4L Hemi SRT, 10.0:1 - 6.4L Hemi Ram trucks
Power: 366-485 hp (273-362 kW) at 4,600-6,000 rpm
Torque: 429-475 ft-lb (582-644 Nm) at 4,000-4,800 rpm
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: 6.7 litres (7.0 qt) with oil filter
Oil change interval: 6,000 miles (10,000 km) or 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
Reliability & Issues
The 6.4-liter 392 Hemi is a reliable V8 engine that produces even more power and torque than the 5.7 Hemi. There have been no serious concerns with this engine in normal daily driving so far. Because it uses the MDS system, the 6.4 Hemi V8 has "Hemi ticking," much like the 5.7-liter version.
Don't be concerned; the tick has no effect on anything. The Cylinder Deactivation System (MDS) needs a thin, contaminant-free 0W-40 oil. As a consequence, only the specified oil should be used, and it should be replaced on a regular basis. The 6.4 Hemi is a massive, reliable American pushrod V8 engine that comes with a five-year or 100,000-mile manufacturing warranty.
In factory condition, the 6.4 Hemi is a fantastic engine that will endure hundreds of thousands of kilometres. On the other hand, the basic 6.4 was never meant to be boosted or pushed to greater power levels. The lowest end of the stock market isn't favourable to this.
Because the pistons aren't forged, there isn't enough material between the rings and the top of the piston. Overheating may also strain the exhaust manifold and cause the studs that hold it together to burst. So the LS series from General Motors isn't exactly forgiving.