Truck History: 1973 Freightliner Powerliner – Its Massive 1150 Cubic Inch Cummins KTA Made It The First 600 HP Diesel Highway Truck

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– Posted on January 20, 2022

Muscle cars were all the rage in the late sixties and early seventies. Truck owner-operators wanted in on the action too, given the low price of fuel and the ability to roll along at 80+ mph on the interstates of the times, never mind passing all the other trucks on every grade.

Freightliner was the only company to create a new truck to meet what was expected to be a growing market with the Powerliner. It came standard with a 400 hp Detroit Diesel V12 (12V71), the CAT 3408 V8 was optional, and the top power option was the 600 hp Cummins KTA-600 with 1150 cubic inches (19 L), a lareg and heavy engine originally not intended for highway trucks. It was the biggest displacement diesel engine ever offered in regular production highway trucks. No wonder the Powerliner had a massive 2000 square inch radiator as well as numerous other changes.

The timing of the Powerliner with its 3 – 4.5 mpg fuel consumption couldn’t have been worse. The 1973-1974 energy crisis resulting in higher fuel cost and the 55 mph speed limit put a serious crimp into its sales, and it was discontinued after a few years. But during its reign, it was truly the King of the Road.

As a frame of reference, the Powerliner (center) was not just a Freightliner COE (right) with a bigger radiator. It had a unique frame whose rails widened at the front to make room for the massive engines. The windshield was larger too, as well as numerous other changes.

In case you’re wondering about the “White” part of its badge, Freightliner for years had a sales and marketing agreement with White that ended in 1975, so the early Powerliners were technically White-Freightliner; the later ones just Freightliner.

As this brochure makes clear, the Powerliner was specifically targeted to owner-operators (“O&O”) and not to fleet operators, who would not have indulged in what were the equivalent of Hemi Chargers for their fleets. The sixties and seventies were the glory years of O&Os, whose share of the trucking market was much higher back then.

Here’s the cab tilted, showing off the standard DD 12V71.

A closer look at that giant radiator and the 12V71.

Although they reflected the best of the times, the interior amenities were anything but luxurious and comfortable. The engine dog house was mammoth, for obvious reasons. I rode in some of these COEs (not Powerliners) in my hitchhiking days, and the noise was absolutely deafening. These were DD 8V71 equipped trucks; the V12 would only have been noisier yet. I did ride in one that had a big CAT six, and it was noticeably quieter, in relative terms.

The Cummins K-series engine, which is still being built today for mining trucks and such, is simply bigger all-round than engines designed for highway trucks. It displaced a massive 1150 cubic inches form its 6.25″ bore and stroke, and it weighed about 4,000 lbs. It came in several versions: KT (Turbocharged) with 450 and 525 hp; KTA (Turbocharged  and Aftercooled) with 600 hp back then, and 700 hp later in its life. There was also a KTTA, with twi-turbos, making some 725 or more, but it was not installed in highway trucks.

According to one source, the only transmissions that were fully warrantied behind the KTA-600 were the 8 and 13 speed Eaton-Fullers, but that may not be accurate.

Speaking of torque, the KTA-600 was rated at 1650 lb.ft., which was top dog at the time, along with its hp rating. But that’s just a jumping off point.

The KTA-600 was also available in select Peterbilt, Kenworth and International trucks. Here’s a charming story from an old 10-4 magazine in 2002, about Mutt Tayman’s KTA-600 Peterbilt that pulled 1007 hp at the rear wheels, thanks to a few tweaks, including twin turbos. And yes, this was his only daily work truck. (Full article here)

At age 15 Mutt started driving a truck – a 1950 Ford F8 that hauled soybeans and corn to Baltimore. In 1958 Mutt purchased a new Ford F8 dump truck, which he used until 1963 when he purchased a 1963 Autocar. Mr. Tayman never liked small engines so he purchased another Autocar in 1967 with an NTC 335 Cummins engine and Fuller 13-speed transmission. Talk about being the “king” – 335 horsepower in 1967!

Now Mutt was on a roll. In 1970 he bought a new Peterbilt with a V-12 Detroit Diesel. Keep in mind that this was a tandem dump truck with 12 cylinders and only three axles. The Peterbilt apparently satisfied his desire for power because he ran this truck for 9 years. In 1979 he ordered a new Peterbilt tractor with a KTA 600 Cummins engine and a 12-5-15-speed transmission. He waited eleven months to get this truck and then picked it up at the Peterbilt factory himself. He apparently didn’t want anyone else to drive his beloved “K” before he got to.

Mutt is still driving this 1979 Pete today. The engine has never been out of the chassis. During the last rebuild, a set of twin turbos and hydraulic variable timing was installed, along with a huge set of injectors and a high volume fuel pump built by Pat Sharp of Diesel Injection of Pittsburgh. This old faded blue Pete produces serious horsepower – 1007 to the ground!

The morning of May 18th, the date of Alban Engine’s Power Day, was cool and rainy. It didn’t take long for the parking lot to fill with beautiful trucks. But the Mutt was cool. He pulled his old Peterbilt through the parking lot and to the side of the building, almost out of sight from the spectators. We had no idea what was under the hood until curiosity got the best of us. Jerry Ray Hairhogger slid under the truck and was shocked to see a twin turbo “K”. Not only was Mutt the oldest owner-operator in attendance, but every other truck outshined his. Mutt’s Pete was a true “sleeper” indeed. This man is so cool he never said a word or showed any emotions – even when his truck was backed onto the Dyno.

After the old Pete was chained and strapped, the shifter was placed in gear and the clutch came out. The dyno rollers started to turn as the spectators watched the horsepower begin to climb. More fuel, more horsepower, more fuel again. The engine roared as the truck shook like a wild animal. As the roar got louder the horsepower continued to climb. When the power hit 1,000 HP the crowd went wild. The top horsepower was 1007 to the rear wheels. That’s somewhere between 1185 and 1258 flywheel horsepower, and well over 3,000 pounds feet of torque through a 1200 pounds feet of torque transmission. This transmission was rebuilt only once in 23 years of driving. You see, when properly driven, high horsepower does not harm the drivetrain.

The KTA-600 became legendary for its ability to make massive power, and ones used in truck pull competitions make up to 3,000 hp, along with prodigious amounts of smoke.

This guy stuffed a KTA into a Dodge Big Horn, and is pretty much unbeatable in that field. These modified engines are run at or close to 4000 rpm, twice their normal peak power speed. The block, crank, rods and pistons are stock.

If that’s a bit too smoky for you, here’s much more laid back and rather sweet video of the shooter’s dad’s original KTA-powered Kenworth. It gives a better idea of how these husky rigs sounded at work in the real world. Basso Profundo.

There’s still a few of these Powerliners out there, increasingly restored and shown at truck shows. If they have KTA power, their value goes up significantly, as not many were originally built that way. That goes even more so for the Peterbilt and Kenworth conventionals.

The KTA’s power was of course eventually surpassed by newer and smaller engines, although 600 hp is still on the high side for a regular highway truck.

But in its day, it was unbeatable, especially so on the grades in the mountains, where it could walk away from any other truck at the time.

The only exception might have been if this 1951 Kenworth with a 600 hp 2181 cubic inch V12 Hall-Scott gas engine. But it didn’t survive long enough to see the coming of 600 hp diesel trucks. What a race that would have been, though.