Straightforward: Ford's Indestructible Inline Six-Cylinder Explained (2024)

Throw as much stock (or shade) as you want at the six-cylinder engine, there is no getting around the fact that it has long been referred to as the Swiss army knife of motors. Be it an angled V6, a brutish Boxer, the Slant-6, or one of the iconic inline six-cylinder designs, drivers the world over have embraced this piston-powered middle ground with open arms.

Nowadays, modern advancements like cylinder deactivation and direct injection have made six-cylinder efficiency better than ever. With twin-turbochargers serving up V8 power figures, the venerated V6, in particular, continues to be lauded as the future of practical performance and power.

But automakers have also begun to show a revived interest in the streamlined, far more rectangular inline-six motor. Even smaller manufacturers like Mazda have recently announced an investment ininline six-cylinder production, proving that the simplified inline-six setup is far from obsolete.

However, in order to appreciate what the modern inline-six has to offer, we should probably revisit the damn-near indestructible Blue Oval iron-block beast that paved the way. For if it weren’t for this American-made slab of simple-yet-effective engineering, who knows where our interest in straight sixes might be…

Forget Ze Germans… Ford Fires On All Six Cylinders

While luxury European automakers may have maintained an interest in the inline six-cylinder more than any other, it was Ford that arguably made the best-selling engine design. An inline six-cylinder success story that was never intended for racing glory or world records, but for mass appeal. Yes, we are referring to the classic Ford 240 and its far larger and brutish brother, the mighty 300.

With its cast-iron overhead-valve cylinder head and block, triple-ringed aluminum pistons, forged connecting rods, hydraulic lifters, and quad-bearing cam, the single-carb six-banger provided reliable power in a much smaller (and affordable) package than the brand’s V8 engines. Naturally, these smaller engines were an instant hit with Ford buyers, with the 240- and 300-cube duo gracing a myriad of platforms starting in the mid-1960s.

A bit of an anomaly nowadays (and not to mention a fire hazard), both 240 and 300 variants featured a non-crossflow head, which directed both intake and exhaust port holes to the same side. However, due to its lower performance potential, the 240 variant was eventually phased out after a decade or so of production, leaving the iconic 4.9-liter 300 to reap all of the rewards.

The larger 300 block sported a beefier bottom end with seven main bearings, and a notably larger 78cc D-shaped combustion chamber design up top. This allowed an 8.8:1 compression ratio to produce more power within each cylinder. On the downside, this also meant that premium pump gas was pretty much mandatory, as anything less typically resulted in detonation and a cantankerous carb.

But whereas horsepower figures remained laughably low, the 300’s performance prowess could be felt within its torque figures, all of which were obtainable upon reaching a modest 1,600 rpm. Considered tepid by today’s standards, the torque found within the Ford 300 was pretty impressive for the time. This made the inexpensive inline six-cylinder engine a go-to option for a broad range of drivers, as well as for businesses that relied upon heavy-duty vehicles.

Straight-Six Staying Power Explained

From 1965, and all the way up until the latter part of the past century, Ford’s straightforward inline-sixer design provided farmhands with the towing and torque they required, and hot rod hellhounds with a readily available and inexpensive high-octane engine swap.

Commercial vehicles and delivery vans also benefitted greatly from the vintage 300, as the torque-rich gasoline motor performed well in cold weather, and hauled heavy loads much like a diesel. Additionally, both compressed natural gas (CNG) and liquefied petroleum gas (LPG) could be used to fuel industrial applications.

With a thicker water pump shaft, robust harmonic dampers, a much larger six-quart oil sump, and a redesigned set of heavy-duty pistons, the late model HD version of the 300 in particular proved to be damn near indestructible when properly maintained.

Furthermore, this engine was the only variant to utilize a steel cam gear design, as opposed to the more lightweight (and far weaker) fiber gears found in non-HD models. Mmmm… fiber-based engine gears. I wonder if Ford originally planned on pairing this dud of a design with its papier-mâché camshafts…

Fast Ford-ward

By 1978, Ford had the 300’s 4.9-liter moniker on lockdown, along with the usage of a simplistic ECU for timing and emission control purposes. This was soon followed by the introduction of an OBD-I diagnostic plug in 1981, which benefited greatly from a widespread conversion to fuel injection in 1987.

With its respectable fuel efficiency ratings (both pre and post-fuel injection introduction), period-appropriate torque figures, and a straightforward design that supported easy servicing and reliability, the 4.9-liter Ford 300 remained widely revered as one of the most reliable inline six-cylinder engines of all time.

Now to see if Ford decides to resurrect the inline six-cylinder Barra it manufactured from 2002 to 2016 for the Australian market…