Curbside Classic: Mack B-20 – Skinny Jeans

1953-1960 Mack B-20 with Fire Truck Grill Surround

When I came upon this Mack B-20 truck in Gaitherburg MD, I couldn’t take my eyes off of it! The shape of the cab is so different from what we see today, and so…small!  I would guess that overall it’s not all that much larger than a 2017 Ford F-350 dually (except for the longer wheelbase), but the look couldn’t be more different.  It is a classically-beautiful design: bold in the front; big wheels to do the work; a subtle, small and minimalist cab that one internet commenter said “you wear like a pair of pants”; and it’s all business in the back with a two range axle.  With such large wheels and muscular flanks, and a small and rounded cab, it’s like a muscle man wearing skinny jeans!

Paul has done an excellent job covering Mack trucks in the past (here and here), but I’ll try to add a unique angle.  In the process of trying to learn more about this truck, I came up with an off-the-wall comparison to another vehicle that you would never imagine to be so similar, as its mission and (I assume) driving experience differ so greatly.  And the most important question is why?  Why do two vehicles with nothing in common look so similar?

Mack Magnadyne EN291 Flathead I6 Engine

They both have an inline 6 cylinder engine, as a major part of the answer! (I’ll reveal the other vehicle further down). This Mack B-20 was the baby of the B-Series, and was delivered with the smallest and least powerful engine, a 291 CI (4.8L) flathead inline six with the tradename “Magnadyne”, making 107hp and 232lb-ft of torque.

Larger B-Series trucks were powered by larger gas and diesel sixes under the name Thermodyne, with sizes up to 707 CI (11.6 liters) for the inline six diesels and 864 CI (14.2 L) for the V8 diesel. And a big 855 CI Cummins diesel six was optional.  No wonder the hood was so long.  And the hood opened in the traditional way, from either side, hinged down the middle.

Now That’s Patina!

From the Mack Truck Section of

Often times, we armchair analysts and critics of current cars say “all cars today look the same.”  My response, strengthened by the analysis of this truck, is that more than we realize, form follows function.  And ultimately the function of our vehicle designs is first and foremost to create an envelope to house the engine and the passengers.

Today, the vast majority of our sedans, crossovers and minivans are front-engine, front-wheel-drive format (excepting most Mercedes, most Cadillacs, all BMWs, and some Chryslers).  And most of the Front-Front designs are transverse engined in a V-configuration (excepting 4 cylinder engines).  Audi has longitudinal, V-configuration engines, Subaru has longitudinal, horizontally opposed engines, and Volvo even has a transverse inline six cylinder, but the design approach is still similar: short and wide sloping hood, leading to a steeply raked windshield.  Trucks, body-on-frame SUVs, and coupes today diverge in design from sedans, crossovers and minivans, and have a more traditional design of front, longitudinal engine and rear-wheel drive.

Curbside Classic Bait:  Can You Keep Yourself from Commenting on This Car?

But if we look backwards to the late 1930s through the late 1940s, there was a completely different “standard configuration” for both cars and trucks of front engine, rear wheel drive, and most engines in an inline design (excepting Ford).  That configuration led to a very traditional looking hood line, long and narrow with a tall grill in the front.  Think of any 1940 Buick, Oldsmobile, Ford or Lincoln, and you can see the hood shape in your mind’s eye.  By the mid 50s, the V-8 became so popular that in due time, American cars would no longer need the long, tall and narrow engine bay required for long-stroke, inline configuration engines, but for the moment, the standard design and look for cars and trucks was similar to the 1940 Chevy Truck.

1940 Chevy Truck

By 1953, most car and small truck designs had moved on from this style of the long, narrow hood with a large upright grill, but big truck design tends to be evolutionary, rather than revolutionary (as Paul reminded me during the writing of this article), so the Mack B-Series didn’t radically alter the looks of its predecessors as much as modify them.  Let’s look at the short lived Mack A Series of 1950-1953,  and the longer lived Mack L Series of 1940-1953, for comparison sake.

1950-1953 Mack A-Series

1940-1953 Mack L-Series (in the same color combo!)

The resemblance is there, especially in the grill, the hood-line, and the bulldog hood ornament, but it’s amazing how much the integrated headlights and fenders, and the smaller, rounder cab with more steeply raked windshield change the look.  According to the forums on, the Mack B-Series featured a widened chassis frame in front for easier maintenance, a wider front axle for improved maneuverability, and rounded fenders with a sleek hood and cab.  The B-Series came in many versions, from B-13 to B-8X, and models built with gas engines had even numbers (B-20, B-42, B-60) while diesel-equipped trucks had odd numbers (B-61, B73).  The total production of the B-Series by 1966 was 127,000, but the B-20 made up only 1,113 examples from 1953-1960, the one I found is really quite rare.

Mack the Bulldog, born in 1921!

It was English Soldiers who first referred to Mack Trucks as Bulldogs, given their tenacious and tough performance in World War I.

So That’s Why They Called It a Bulldog!

Although I think the looks of the truck to which they were referring, the Mack AC, clearly contributed the bulldog nickname.

Just Enough Room to Drive

But back to the B-20:  In the spirit of Paul’s post entitled Did The Lincoln Mark IV Have the Biggest Overhang Ratio Ever?, I ask has there ever been a truck with a smaller cab to hood ratio?


King Ranch Edition It Is Not

The B-20 cab was also quite minimalist.  No heat or air conditioning, and you can see the road through the floor where the shifter rises from the transmission.  Neither power steering nor syncro-mesh, nor suspension system in the seat.  Just a basic working environment.

Ok, I’ve stretched out the reveal of my off the wall comparison long enough.  The drum roll has begun to lose its power, and so without further explanation, I’ll share the vehicle the B-20 most reminds me of, another vehicle with an evolutionary design, with a long-stoke inline six engine:  The Rolls Royce Silver Cloud I.

Rolls Royce Silver Cloud I (courtesy of Paul N.)

When You Squint, You Can See the Similarity!

Isn’t it amazing how much these incredibly different vehicles look alike?  The Mack B-Series looks to me almost like a Rolls Royce with more modern, flush-mounted headlights.  And, as the B-Series came out in 1953, and the Silver Cloud I in 1955, the Mack B-20 is obviously not copying the looks of the Roller.  The B-20 at the time did not have the chrome grill surround, except on the fire truck version, and without the surround, the resemblance is greatly diminished.  Nonetheless, the way the grill stands up, the hood-line flows back into the cabin, and the roundness of the roof-line are so much more similar than one would expect.  And back to my theory as to why…

Rolls Royce 4.9 Liter Inline 6

That’s right, until the Silver Cloud II in 1959, the Rolls Royce Silver Cloud ran a long-stroke, overhead-valve inline 6 cylinder, which contributed greatly to its long hood and upright grill.  The Silver Cloud engine traced its overhead valve lineage all the way back to the Rolls Royce Twenty of 1922-1929 which ran an OHV Inline Six of 3.1 Liters.  The 4.9L as installed in the Silver Cloud I is listed by wikipedia to have 155hp at 4,000 rpm, as compared to the B-20’s horsepower peak of 2800 rpm.  I would imagine the Silver Cloud to be a much different driving experience, despite the Silver Cloud’s live axle and leaf springs in the rear.

And so with no more similarities to share, I’m left only to present the rest of the pictures of this beautiful truck, and to wonder how any vehicle this functional came to be this beautiful…

The Business End

The back of the cab looks less modern and less British than the front to my eyes.  No creased character lines like the Rolls Royce; more of a pre-war American look, like a 1938 Chrysler Imperial Limosine.

Now That’s How You Do a Bustleback!

Speaking of the business end, I just have to show more pictures of this beautiful truck for those who are interested.

I Count 16 Leaves…

Are any of our readers qualified to share more about the capabilities, professional uses and driving experience of this incredible truck?

Front Drop Axle

I’m nearly done, just finding excuses for the final pictures…

Reduction Gears?

I’m so curious to hear what Paul or anyone else can share about the functional design of these trucks…


Well our tour of this antique Mack truck is almost over.  Please forgive my inadequacy to the task of presenting its capabilities, but I hope the pictures alone are worth the journey!

Woof Woof!

Happy Trails!

And so slip into these skinny jeans,  give the engine a rev, pop the transmission in gear, wrestle that steering wheel, and see if you’ve got what it takes to drive the bulldog!


Mack R-Series

Mack DM Series 4×4