- Story By Benjamin Hunting
The V8 engine has long been the focus of almost every classic truck or SUV enthusiast. In the 1960s and '70s, however, six-cylinder motors found their way between the front fenders of almost every pickup or sport-utility on the market, often as the affordable entry-level option. This means that there are thousands of V6 and straight-six trucks out there waiting to be discovered by someone willing to accept them as they are, rather than use them as a template for building yet another eight-cylinder clone.
Which classic six-cylinder trucks are worthy of the most attention? Check out these 'big sixes' that offered nearly as much utility and torque as the V8 motors that would come to replace them in the popular consciousness.
GMC 305 V6
Right up until the end of the 1950s, if you wanted a six-cylinder engine in a truck it had to be an inline-six.
That all changed in 1960 when GMC introduced a 305 cubic inch V6 that was specifically designed for use in pickups and other heavy-duty vehicles. The engine was intended to handle extreme use while providing the kind of torque that pickup owners asked for.
With 5.0L of displacement and up to 165hp and 280 lb-ft of twist, the new V6 was more than adequate in an era when trucks were rarely used as daily drivers. Aluminum pistons and hefty bearings were some of the highlights of the 305 V6, which would pull duty as the entry-level engine in not just half-ton pickups but also the GMC Suburban all the way until 1974.
AMC 258 I6
American Motors Company had a long history of building stout six-cylinder engines. Of these, one of the most enduring was the 258 cubic inch design offered under the hoods of a long list of both trucks and passenger cars from 1971 to 1990.
The engine, which was also known as the 4.2 (its displacement in liters), produced between 110 and 150 horsepower depending on its application and was good for as much as 240 lb-ft of torque.
For SUV fans, the most popular models featuring the AMC 258 included the Jeep Wagoneer and Cherokee, the J-Series pickups, and of course the CJ and the Wrangler YJ that replaced it, which would pick up the 258 from 1987 to 1990. International Harvester would also borrow the engine to install in the Scout for most of the 1970s.
Ford 300 I6
Ford's 300 cubic inch inline six was relied on for 30 years by truck, van, and SUV owners seeking an extremely reliable engine that could still tow a trailer or haul a heavy load without consuming too much gas. Introduced in 1965, the 300 represented the fourth generation of Ford's I6 evolution, and it ended up being such a strong design that it was the final and most enduring straight six motor that the Blue Oval would offer in North America.
Ford produced many different varieties of the 300 across a wide range of industrial applications, but on the automotive side it would offer as much as 150 horsepower when fuel injection entered the mix in 1987 (having delivered about 100 horses when it first went on sale). Torque was strong, topping out at 260 lb-ft, which allowed it to find a home in both the F-150 and heavy equipment such as medium-duty trucks weighing as much as 20,000 lbs.
Dodge 225 Slant Six
The 225 cubic inch version of Mopar's famous 'slant six' engine (so named because its inline cylinder arrangement sloped to one side to clear the hood in passenger cars) was a solid stand-in for Dodge truck buyers for more than two decades.
With horsepower similar to the slightly larger Ford 300 (145 horses in its most potent tune), the 225 appeared in 1960 and quickly developed a similar reputation as an unkillable engine. On top of its refusal to say die, Dodge pickup owners were fond of its miserly ways at the fuel pump, which made it particularly popular throughout the 1970s when gas prices became a major concern for anyone owning a V8.
Patience was a virtue with the 225: by the time it left the market in 1987 (replaced by the 3.9-liter Magnum V6), its 96 horsepower and 170 lb-ft of torque had made acceleration a gradual process at best.
GMC 478 V6
Our round-up of big sixes began with GMC and it's ending with GMC, too. In fact, the massive 478 cubic inch V6 that the company debuted in the 1960s was a direct evolution of the original 305 motor from just a couple of years beforehand.
Massive doesn't begin to describe the 478, which was larger in terms of displacement than many V8 engines of its era. With an astonishing 442 lb-ft of torque on tap to complement its 254 horsepower, it's no surprise that GMC intended the motor for use in heavy-duty dump trucks, haulers, and buses.
Not a performance engine by any stretch of the imagination, the 478 was intended to live its life at low revs and earn its keep in an industrial setting. Some were even repurposed as generators or used to power equipment in factories and sawmills, or pump water out into the fields as part of massive agricultural irrigation systems.
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Insights, advice, suggestions, feedback and comments from experts
As an expert and enthusiast, I have personal experiences or beliefs, but I can provide you with information on the concepts mentioned in this article. Let's discuss each concept in detail:
A V8 engine is a type of internal combustion engine with eight cylinders arranged in a V configuration. It is known for its power and performance, making it popular among enthusiasts and in high-performance vehicles. The V8 engine has been a focus of classic truck and SUV enthusiasts for a long time.
In the 1960s and '70s, six-cylinder engines were commonly used in pickup trucks and sport-utility vehicles (SUVs) as an affordable entry-level option. These engines provided utility and torque comparable to V8 motors. Here are some notable six-cylinder engines mentioned in the article:
GMC 305 V6: In 1960, GMC introduced a 305 cubic inch V6 engine specifically designed for use in pickups and heavy-duty vehicles. It provided torque and durability, making it suitable for truck owners. The GMC 305 V6 was used as the entry-level engine in half-ton pickups and the GMC Suburban until 1974.
AMC 258 I6: The AMC 258 cubic inch inline-six engine was offered by American Motors Company from 1971 to 1990. It was used in various trucks and passenger cars, including the Jeep Wagoneer, Cherokee, J-Series pickups, CJ, and Wrangler YJ. The engine produced between 110 and 150 horsepower and had good torque, making it popular among SUV fans.
Ford 300 I6: Ford's 300 cubic inch inline-six engine was introduced in 1965 and became the most enduring straight-six motor offered by Ford in North America. It was known for its reliability and towing capacity. The Ford 300 I6 was used in trucks, vans, and SUVs, including the F-150 and medium-duty trucks. It produced up to 150 horsepower and had strong torque, reaching 260 lb-ft.
Dodge 225 Slant Six: The Dodge 225 cubic inch 'slant six' engine was used in Dodge trucks for more than two decades. It was known for its durability and fuel efficiency, making it popular during the 1970s when gas prices were a concern. The engine produced 96 horsepower and 170 lb-ft of torque. It was eventually replaced by the 3.9-liter Magnum V6 in 1987.
GMC 478 V6: The GMC 478 cubic inch V6 engine was a larger evolution of the original 305 motor. It was designed for heavy-duty applications such as dump trucks, haulers, and buses. The massive engine produced 254 horsepower and an astonishing 442 lb-ft of torque. It was not a performance engine but excelled in low-rev, industrial settings.
These six-cylinder engines offered utility and torque comparable to V8 engines, making them worthy of attention for classic truck and SUV enthusiasts.
I hope this information helps! Let me know if you have any further questions.