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Fixing a heavy-breathing Hemi

Monday, February 26, 2018 - 09:00
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In our shop we don’t see many Chrysler cars, but we do see a bunch of Jeeps, minivans and Ram pickups. Most of the Ram pickups in our area are sold with the “Hemi” motor in them so our chance of seeing one of them is going to be on the high side. One of the most important services that needs to be performed on this powerhouse of an engine is an oil and filter change. As we know, there are many vehicle owners who shop for the cheapest oil and filter change prices. Well, shopping for the cheapest oil and filter change usually is going to cost them in the long run. The old commercial from FRAM, “Pay me now or pay me later,” really applies, especially with these engines. Before we dive into our case studies of heavy-breathing powerplants, we need a short history lesson of where the motor came from and the changes that make it today’s Hemi engine.

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The Muscle Car era

Chrysler made their first engines with hemispherically-shaped combustion chambers in 1951, but these early motors ranged from 301 to 392 cubic inches. They were called the “Red Ram,” “Firedome” and “Firepower,” depending on brand and horsepower peaked in 1958 with a dual four barrel version of the 392 rated at 390 hp, which would soon be outperformed by a 413 Wedge.. inches. They were called the “Red,” “Firedome,” and “Firepower,” depending on brand and horsepower peaked in 1958 with a dual four-barrel version of the 392 rated at 390 hp, which would soon be outperformed by a 413 Wedge.
When the 426 Hemi was introduced in 1964, it was strictly a racing engine.

That same year, four Hemi-powered Mopars swept the Daytona 500, finishing 1-2-3-4. It caught the racing world by surprise, and prompted NASCAR to impose stricter production rules on Chrysler. Instead of producing a few blueprinted Hemi motors each production year, they would have to produce several thousand and sell them in street-legal cars. The street Hemi soon showed up in select 1966 Dodge and Plymouth models. to impose stricter production rules on Chrysler. Instead of producing a few blueprinted Hemi motors each production year, they would have to produce several thousand and sell them in street-legal cars. The street Hemi soon showed up in select 1966 Dodge and Plymouth models.

Today, it’s a different story. Chrysler has their Dodge Challenger Demon 6.2L engine producing 840 horsepower that will clock a 0 to 60 mph run in 2.6 seconds. Since most of us won’t be so lucky to work on or even drive one of the 6.2L Demons, it’s time to get back to reality and concentrate on the Hemi that we are most likely to work on. The engine that I am referring to is the 5.7L Hemi that is the most common along with its sister 6.1L engine that is similar. Starting in 2003, the Hemi was used in the Dodge Ram 1500, 2500 and 3500 pickup trucks as well as their Dodge Durango, Chrysler 300C, Dodge Magnum R/T, Jeep Grand Cherokee, Dodge Charger R/T and Dodge Challenger R/T. The Hemi comes in different flavors such as a straight up standard engine, Variable Camshaft Timing (VCT) or Multi-Displacement System (MDS). Having owned a Chrysler 300C with the 5.7 Hemi that utilized the MDS, I can tell you that this engine can produce some ass-kicking horsepower. I maintained my 300C properly and changed the oil using the specified oil and had absolutely no problems with the engine, so my Hemi was breathing just fine. Now that we have covered some of the Hemi’s history, let’s move on to some real-world breathing problems.

A Hemi with a problem

Let me share our New York experience with Hemi breathing problems that we encountered in our shop. First is a 2009 Dodge Ram 1500 pickup, equipped with a 5.7 L Hemi and with 112,962 miles on the odometer. It came in with a concern of low power and performance. The vehicle owner said that she had always taken care of her Ram and had the oil changed every 3,000 miles. She proceeded to tell us that she had all the recommended work performed by her former technician.

We assured her that we would perform a thorough inspection of her vehicle to address her concerns. Since this Ram’s check engine light was illuminated and there was the complaint of a performance problem, we explained the steps we would perform. These steps would include a complete vehicle scan, along with testing the engine’s mechanical condition. I had Bill, my lead tech, scan the vehicle’s computer system, where he discovered a P0305 (Cylinder #5 Misfire) that could be the result of a mechanical, ignition or fuel problem.
 

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