News

Jan 30, 2024

10 Worst Inline

The inline-six is arguably the most reliable way to arrange six cylinders under

The inline-six is arguably the most reliable way to arrange six cylinders under the hood, but some inline-six engines belong in a junkyard.

The straight-six engine was the engine of the 20th century. If you wanted power with fuel efficiency, you would forgo the V8 and choose the straight-six.

Engine technology and manufacturing techniques have come a long way. Even so, reliability issues, lack of power, and other problems plague some straight-six engines. Most modern engines are smaller straight-fours and turbocharged. Emissions regulations, climate targets, and different consumer demands mean that these engines may soon become a relic of the past.

Still, tuning, repairing, and reusing are in line with such targets. So, if you're looking for a straight-six engine on the used car market or a new one, these are the ones to avoid.

As far as 60s engines go, the Triumph "Six Cylinder" is not the most unreliable. It has two major issues though. The crankshaft is a four-main-bearing crank. This means it can't take more power than stock and is prone to scoring. It won't break all at once, but once the thrust washers are worn, you might your crankshaft in the oil sump.

Another issue with the TR6 is the fuel injection system. Fuel vaporization in the fuel lines causes an issue called vapor lock. The original mechanical fuel pump operates at low pressures which cause liquid fuel to turn into gas before reaching the engine. Of course, head gasket issues are also present, but those are mostly age-related.

Related: 10 Worst Engines Ever Put In A Sports Car

It's a diesel, it's reliable, right? Wrong! Early versions suffered from HPFP issues, EGR valve failure, and high oil consumption just to name a few. It was BMW's first attempt at a diesel engine, so it is expected to have issues.

It also has some serious issues with overheating. During prolonged operation, the engines are prone to catching fire. This was the case for X3 police vehicles in the U.K. in 2022. Top-spec cars with intercoolers are less prone to this problem, but it is a common issue on the NA version of this engine.

Toyota rarely makes a bad engine. They are cautious when it comes to tech, and produce cars that last a lifetime. However, Toyota incorrectly torqued the head bolts on this engine. Almost all 7M-GTEs are prone to head-gasket failure.

The block is strong, but the internals not so much. Rod knock is common on these engines and will cause catastrophic failure. The original cooling system and oil pump are just not up to the job as well. Toyota would fix these issues with the 1JZ and 2JZ, which is why almost everyone swaps these engines into their MK3 Supras.

Related:10 Worst V6 Engines Ever

Nissans are not known for their reliability. The P40 is an exception. It's a 50s OHV engine that Nissan continued to use until the late 90s. Even worse, the engine is based on a pre-WW2-era design. So, by the time the 90s rolled around, it was underpowered even when compared to the other worst Japanese engines of the time.

It's best known for powering the Nissan Patrol. You'll still find these trucks chugging along in Ecuador, Cuba, Mozambique, and India. Unfortunately, 123 hp is just not enough to power heavy trucks.

Thanks to the notorious I.M.S. bearing failure, Porsche ownership can sometimes be a pain. Early versions of the M96 suffered from block-sealing issues. The metal composition caused moisture to seep into the block and mix with oil.

It also suffered from rear main seal failures. A lot of these issues were fixed in later versions, and some owners never encountered these issues at all. Even today, neither Porsche nor its owners know the exact conditions that cause these issues. However, it's enough that most people should avoid cars with these engines.

Most people will remember the iconic 2.4-liter and 3.8-liter versions of this engine, which were extremely reliable. With this engine, everything that could be cut was cut. To save costs, they bored the 1950s engine out to make more power. This thinned the block which lead to more quick fixes like drilling cooling passages into it.

These engines are notorious for blowing head gaskets, head stud corrosion, and engine block cracking. In the 80s plastic was even more susceptible to heat. Plastic housings, intakes, and seals become brittle and ultimately cause the engine to fail.

Related: 10 Worst Four-Cylinder Engines Ever

AMC is a name that defined the muscle car era. They made some good cars with terrible engines. One of which being the AMC 3.2-liter Straight-Six engine. It suffered from overheating issues, gasket failure, and head bolt issues.

Despite having forged internals, the engine had so many design flaws. It required head bolts to be torqued every 5000 miles just to keep it running. You would end up with catastrophic failures even when following this. Ironically, these engines were also used in Jeeps, which even today are known for their engine issues.

A lot of early engines are underpowered compared to their modern counterparts. The Chevy 3.8-liter Turbo-Thrift engine was underpowered even for its day at a peak of 150 hp. Emissions regulations meant that Chevy had to reduce power. Its lowest rating was 90 hp.

Reliability was also a concern if you owned a car with this engine. The exhaust and intake were on the same side of the engine, so heat soak would cause power loss damage over time. Most people remember its predecessor, the Stovebolt, and think this engine is just as good. It's not.

If you're looking at a Z-car, you've probably heard of this engine. The L28E is the turbocharged variant and is popular with tuners. The NA version though, best known for powering the Nissan Patrol 160, is one of the worst six-cylinder engines.

Underpowered at 118 hp, it's known for reliably chugging along, albeit very slowly. The engine would get electronic fuel injection and improved internals but would be replaced by the CA engines. Of course, another underpowered engine, the P40, also powered the patrol.

While some owners love and swear by the BMW N54 engine, others have gone completely bankrupt trying to keep them running. Later versions fixed almost all major issues and only required regular maintenance to keep them running. Early versions suffered from turbo gasket failure, water pump failure, heat soak, and valve cover gasket issues among others.

The engine in general requires a lot of technical knowledge to maintain properly. Gaskets and seals need specific lubrication, and valve covers are a consumable part. Although most people complain about the High-pressure fuel pump issues, these can be mitigated by using an aftermarket pump or upgrading cooling.

Nathan has a keen interest in tech. Essentially living and breathing technology. However, one of his hobbies happens to be car therapy. He falls asleep in cars all the time. He loves driving them, writing about them, and watching car Youtube. Maybe he loves cars a bit too much.Of course, like Nathan, this bio exudes positivity. Nathan's personality and life direction can be put down to that single word, positivity.As a writer, Nathan always wants to improve. He excels in an environment where he can create good content and deep-dive into topics.