![]() More or less fuel can be released when the next intake valve opens. The main advantage of a sequential system is that the entire system has a fast response time when the driver makes a quick change. While sequential variable fuel injection has many benefits, direct injection is quickly becoming the system of choice and is replacing the SEFI systems. Other multi-port systems will fire all the injectors in groups no matter if the cylinder is ready or not. So in essence, the individual injectors work by themselves because they are fired individually. So, it's not like GM's LS series that is more forgiving.A sequential fuel injection is a type of multi-port fuel injection system in which each injection valve will open just before the cylinder intake valve opens. Also, the exhaust manifold may twist from overheat and burst the studs of its fastening. The pistons are not forged and there is not enough meat between the ring lands and the top of the piston. The stock bottom end is not good for that. But, the stock 6.4 is by design not built for boost and pushing more power. ![]() In stock form, the 6.4 Hemi is a great engine that lasts and serves hundreds of thousands of miles. 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. Therefore, it is very important to use only the recommended oil and change it on time. The Cylinder Deactivation System (MDS) needs thin 0W-40 and clean oil. Don't worry, "the family's tick" does not affect anything. Similar to the 5.7-liter version, "Hemi ticking" is found on the 6.4 Hemi V8, as it also has the MDS system. To date, there were no known serious problems with this engine in normal daily-drive usage. Like the 5.7 Hemi, the 6.4-liter 392 Hemi version is a good, reliable V8 engine with even more power and torque. The truck 6.4 Hemi ran on 89 octane gas, but also capable of running on standard 87 octane gasoline.Ĭhrysler/Dodge 6.4 Hemi Common Problems and Reliability It also cuts out the valve lifters for those cylinders in order to eliminate pumping losses. When power is not needed, like on a highway, the system turns off the fuel in four cylinders. Valvetrain features hydraulic roller lifters and sodium-filled exhaust valves.įor 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. The 6.4L truck engine has a cam-in-block variable valve timing (VVT) which uses a hydraulic cam phasing system developed by Chrysler. Both versions come with drive-by-wire throttle bodies. ![]() 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. 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). They have two valves and two spark plugs per cylinder (16 total) and oval-shaped, semi-hemispherical combustion chambers. 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.Ĭylinder heads are similar to the late 5.7 Hemi heads. This is one of the reasons why 6.4 Hemi V8s come with an oil-to-water oil cooler. Oil jets, or squirters, spray engine oil on the bottom of each piston to remove combustion heat. The 6.4 Hemi engine block features piston cooling jets. ![]() Like in the 345 Hemi, the main bearing caps are cross-bolted. The new 392 HEMI comes with a forged steel crankshaft. ![]() However, these two engines don't share neither bore diameter nor stroke size. 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. ![]()
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