The Ultimate Workhorse Showdown: GMC 305 V6 vs Ford 300
The GMC 305 V6, the Ford 300 inline 6.
Two engines, same displacement, same era, same mission.
One was a revolutionary V6 that GMC engineered from the ground up.
Overbuilt, innovative, and powerful enough to shame V8 engines twice its size.
The other was an inline 6 so indestructible that after 31 years of production, Ford still could not build anything better.
One was discontinued before its prime.
The other refused to die for three decades.
Both earned reputations that still start arguments at car shows.
And today we are settling it.
This is the showdown 60 years in the making.
The clash of two philosophies, two companies, and two engines that defined what it meant to work for a living.
By the end of this video, you will have everything you need to decide for yourself which engine reigns supreme.
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Now, let’s start with the GMC 305 V6 because this engine was truly revolutionary when it hit the scene in 1960.
GMC wanted their own unique identity separate from Chevrolet and they delivered.
The 305 displaced 304.6 cub in or 5.0 L if you are counting with a bore of 4.25 in and a stroke of 3.58 in.
What made this engine special was its 60° V6 configuration.
Because that 60° angle combined with a sixth row crankshaft created one of the smoothest running engines you could get without needing a balance shaft.
It was engineering brilliance.
This was a purpose-built truck engine designed from the ground up.
The GMC V6 family would eventually grow to include the 351, 401, 478, and even the massive 702 cubic in V12 twin 6.
But the 305 was the baby of the family and it was the workhorse for lightduty applications.
Now let’s talk about the engineering.
This engine was overbuilt.
We are talking aluminium pistons, massive bearings, the same bearing sizes used all the way up to the four 78 cubic in diesel versions, seven main bearings, and spark plugs positioned on the inboard side of the heads.
GMC said this kept the plugs away from hot exhaust manifolds and made them easier to access.
The reality was smart packaging.
The oil pump on this engine could flow 14 gall per minute.
The water pump could move 135 gall per minute.
That is an insane capacity for an engine this size.
And it tells you GMC designed it to work hard in tough conditions and not overheat or starve for oil pressure.
One really cool feature was the use of timing gears instead of a chain or belt.
That meant no timing chain to stretch or break, just durable metal gears that could outlast the rest of the truck.
The high-mounted cam shaft sat in a bath of oil constantly, which meant you could not dry scuff it even if you wanted to.
The 305 V6 was GMC’s standard pickup and Suburban engine from 1960 to 1969, and you would find it in 1,00 through 3500 series trucks.
After 1974, GMC discontinued the V6 family entirely and switched to Chevrolet inline 6s and V8s.
But during its run, the 305 earned a reputation as one of the toughest, most reliable engines GM ever built.
Now, let’s talk about the Ford 300 inline 6.
This engine is also legendary.
It ran from 1965 all the way to 1996, making it one of the longest production runs of any American gasoline engine.
31 years of continuous production.
That alone tells you something.
The Ford 300 displaced exactly 300 cub in or 4.9 L with a 4-in bore and a 3.98 in stroke.
It was actually based on the smaller Ford 240 inline 6 sharing the same bore but with a longer stroke.
The two engines were so similar that the heads were interchangeable.
Like the GMC 305, the Ford 300 used timing gears instead of a chain or belt.
This was old school engineering at its finest.
Bulletproof reliability with no maintenance headaches.
The engine featured seven main bearings which gave it incredible bottom-end strength and smoothness.
Early carbureted versions of the 300 made around 170 horsepower in the late 1960s.
But by 1972, when Ford switched to SAE net ratings, the numbers dropped to around 119 to 122 horsepower.
Do not let those numbers fool you, though.
This engine was never about horsepower.
It was all about torque.
The 300 produced 260 to 265 lb feet of torque in its fuel injected versions.
And here is the kicker.
Most of that torque came on strong, starting around 2,000 revolutions per minute, perfect for truck work.
In 1987, Ford introduced fuel injection to the 300, bumping output to 150 horsepower at 3,400 revolutions per minute and 265 lb feet of torque at 2,000 revolutions per minute.
The fuel injection improved reliability even more and gave better fuel economy and cold start performance.
The heavyduty versions of the 300 found in larger commercial trucks in the 15,000 to 20,000lb range came with forged crankshafts and connecting rods, high- flow heavyduty exhaust manifolds, and beefier internal components.
These heavyduty engines were constantly working in the 3,000 to 4,000 revolutions per minute range and barely broke a sweat.
One of the coolest things about the Ford 300, it was used in everything.
Yes, F-S series pickups and Broncos and Econoline vans, but also tractors, wood chippers, ski lifts, power generators, sawmills, airport baggage tractors, and most famously UPS delivery trucks.
If you got a package from the big brown truck in the 80s and the ’90s, chances are it was powered by a Ford 300.
The engine’s simple design, cast iron construction, and robust internals meant it could handle serious abuse.
It is not uncommon to find these engines with 300,000 to 500,000 mi still running strong with nothing more than regular oil changes.
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All right, let’s get into the nitty-gritty comparison.
How do these engines stack up head-to-head?
For displacement, the GMC 3005V6 displaced 305 cub in 5.0 L.
The Ford 300 inline 6 displaced 300 cub in 4.9 L.
Pretty much dead even on displacement.
The GMC has five more cubic in which is negligible in horsepower.
The GMC 3005 was rated from 150 to 170 horsepower depending on the variant.
The Ford 300 was also rated from 150 to 170 horsepower depending on the version.
Again, virtually identical.
Neither engine was designed to be a powerhouse.
They were designed for work.
Here is where it gets interesting.
The GMC makes its torque at slightly lower revolutions per minute from 1,400 to 1,600 revolutions per minute compared to the Ford at 2,000 revolutions per minute.
That is a realworld advantage for the GMC in low-speed pulling and lugging situations.
Torque at the low end matters.
In configuration, the GMC was a 60deree V6 with a sixth throw crankshaft, while the Ford was an inline 6.
The Ford has an inherent advantage here because inline sixes are naturally balanced engines.
They are smoother than almost any other configuration.
The GMC 60° V6 with a sixth throw crank was smooth for a V6, but physics is physics, and the inline 6 is going to be smoother.
In dimensions, the GMC has a clear advantage.
The V6 configuration is more compact than an inline 6.
The Ford 300 long inline layout took up a lot of space under the hood, which could make some repairs more challenging.
The GMC V6 was shorter and more packable, giving you better access for maintenance.
Weight.
The GMC 3005D weighed around 795 lbs dry.
The Ford 300 weighed in the same ballpark.
No significant advantage either way.
Fuel economy.
Here the Ford shines.
With proper gearing, many F-150s and Broncos with the 300 could achieve 18 to 22 mp gallon on the highway.
Ford even advertised 30 m per gallon in some literature, though that was probably optimistic.
The GMC V6, while efficient for its time, was known as more of a gas drinker, probably in the 12 to 15 mp gallon range for most applications.
The Ford’s inline configuration and its longer production run with fuel injection gave it a real advantage in efficiency, which became increasingly important through the 70s and the 80s.
By the end, you will have the facts and practical pros and cons to choose your side in the rivalry.
Vote and share your stories in the comments.
Let’s talk about realworld ownership.
What’s it like to actually work on these engines?
The compact V6 design of the GMC 305 means better access in the engine bay.
You can actually reach most components without contorting yourself.
Inboard spark plugs take a little getting used to, but once you figure out the access, they are easier to get to than you would think.
Timing gears mean you never worry about timing chains or belts.
Oil changes are straightforward.
The biggest challenge is parts availability.
Finding gaskets, bearings, and hard parts requires more hunting than with the Ford.
Specialty suppliers and the 6066 GMC enthusiast community are your best friends.
The engine’s design with four ringed pistons, three compression rings, and one oil ring was ahead of its time.
The high-mounted cam meant no special break in procedures or worry about cam failure.
Ford 300 inline 6, on the other hand, is almost criminally easy to maintain.
Everything is laid out in a row.
Plugs, wires, and valves are all in a straight line, so you work your way down the line.
There is no valley to reach into and no tight spaces between cylinder banks.
The long inline configuration does mean it takes up a lot of room, which can make things like water pump replacement or oil pan work more challenging in some applications.
But for regular maintenance, plugs, oil changes, and tuneups, it is as simple as it gets.
Parts availability is excellent even today.
Aftermarket support is huge.
You can even get performance parts such as cams, headers, and intake manifolds if you want to hop one up.
The single barrel carburetor on older models is dead simple to rebuild.
The fuel injection on later models is reliable and easy to diagnose.
Beyond the specs and the nuts and bolts comparisons, what’s the legacy of these engines?
The GMC 3005 and the broader V6 family represent one of the most innovative periods in GMC’s history.
Before the brand became basically a rebadged Chevrolet with more chrome, GMC built their own engines, their own identity, their own legendary machinery.
The 3005 was America’s first production V6 in a truck.
It proved that six cylinders in a V configuration could deliver V8 like characteristics with better efficiency.
It paved the way for every modern truck V6 we see today.
The engineering was brilliant.
That 60° angle, the sixth throw crank, the massive oiling system, the overbuilt construction.
GMC did not cut corners.
They built an engine that would represent their brand’s work ethic.
The GMC V6 family powered some of the most important working vehicles of the 60s and the 70s.
School buses full of kids, delivery trucks bringing goods across America, dump trucks building our infrastructure.
This was not an engine for show.
It was an engine for work.
The Ford 300 is, without exaggeration, one of the most important engines in American automotive history.
Its 31-year production run influenced an entire generation of truck buyers.
People bought Ford trucks because of the 300.
This engine won the Baja 1,3 times.
It powered the trucks that built America’s farms and ranches.
It delivered packages, towed trailers, hauled materials, and generally did the unglamorous work that keeps society running.
The Ford 300 proved that you did not need a V8 to be a real truck.
It showed that properly designed, a six-cylinder could be more reliable, more efficient, and more practical than engines with more cylinders.
The engine’s simplicity became its greatest strength.
In an era when vehicles are increasingly complex and difficult to repair, the Ford 300 represents something we’ve lost.
Mechanicals that anyone with basic tools could maintain and repair.
When Ford discontinued the 300 in 1996, they ended the last American inline 6 in a production truck.
Many enthusiasts consider this the end of an era.
So, here we are.
All the facts are on the table.
Two legendary engines, each with its own strengths, philosophy, and place in history.
The truth is both of these engines represent American bluecollar engineering at its absolute finest.
The GMC 3005 was ahead of its time.
A brilliant piece of engineering that proved V6 engines belonged in working trucks.
The Ford 300 was engineering perfection through simplicity and relentless refinement.
If GMC had continued developing the V6 family for another 20 years like Ford did with the 300, we might be having a very different conversation today.
But history went the way it went.
