If Mopar guys are a different breed, then the ones fixated on the
Slant Six "tower of power" might just as well be from another planet.
So when we found out about a wacko Slant Six 1974 Plymouth Duster with
rear-mount turbo system prowling the backroads of North Carolina, we
figured the owner would come off something like Brad Pitt's character in
12 Monkeys, and that we'd have to make sure he took his meds before meeting us.
2/12
Time has also proved the Slant Six to be durable as all get-out, and
its all-cast-iron construction and low compression ratio make it an
ideal candidate for forced induction. For that, Brian kept true to the
project's unconventional nature and consulted Squires Turbo Systems, the
company known for unorthodox rear-mount designs. Mounting the
turbocharger out of the engine compartment drastically reduces underhood
temperatures, which allows for lower intake air-charge temps and makes
changing jets and tuning changes on the carb much easier on a hot
engine. It also made the project more attainable and practical, because a
custom exhaust manifold wasn't required. In the Duster, the
turbocharger is mounted just behind the rear axle, and the stock fuel
tank was replaced with an offset fuel cell to make room for it.
3/12
After more than three years' work, Brian says the turbo Duster
matches his original vision perfectly. He also made good on the plan to
run it on the strip, where it has delivered a best e.t. of 15.40 at 90
mph—with a race weight (including driver) of 3,600 pounds. In an era of
1,000hp, LS-powered street cars, that's hardly an impressive
quarter-mile time, but when it comes to originality and ingenuity, the
Duster has them beat by a country mile.
4/12
Tech Notes
Who: Brian Mimken
What: 1974 Plymouth Duster—aka "Sixy Beast"
Where: Etowah, NC
Engine: The original tried-and-true, 225ci Slant Six features 0.030-over pistons, a stock forged crankshaft and stock rods. Compression is kept to a boost-friendly 8.4:1, and the stock cylinder head was treated to a three-angle valve job and fitted with 1.70/1.44-inch stainless valves. The camshaft is a Mopar Performance "244" stick, with 244 degrees of duration and 0.436/0.436-inch lift. Squires Turbo Systems supplied the GT35 turbocharger, which is mounted behind the rear axle and blows about 7 pounds of boost through a Holley 390-cfm 4-bbl, modified for forced induction, into an Offenhauser aluminum intake manifold. A pair of Clifford Slant Six shorty exhaust headers feeds a 2.5-inch flow tube to the turbo, with exhaust routed to a 3-inch outlet. An air-to-air intercooler adapted from a late-model Nissan 350Z helps cool the intake charge. The engine also uses the stock distributor, along with an upgraded coil and a timing retard controller. All told, the turbocharged tower of power produces 250 hp and 330 lb-ft of torque. Don't snicker—that's a 240 percent increase in horsepower and a nearly 185 percent jump in torque over the stock 105hp/180–lb-ft output.
Transmission: The stock slushbox probably wouldn't have been capable of handling the high-pressure Slant Six, so Cope Racing Transmission built a street/strip version of the A904 three-speed automatic and fitted it with a 2,500-stall PTC torque converter, which helps the Duster get off the line quickly.
Rearend: Nothing trick here—just proven, durable components, including a Mopar 83⁄4-inch axle fitted with a Sure Grip limited-slip differential and 3.23 gears.
Suspension: Who knew Hotchkis made handling parts for Dusters? This car's got 'em, including front adjustable upper control arms and a thick, 1.25-inch sway bar. There's also QA1 shocks up front, along with the stock torsion bars. In the rear, it's the stock leaf springs, QA1 shocks, and a Hotchkis 1-inch sway bar.
Brakes: Factory-style 11-inch disc brakes up front and simple 10-inch drums in the rear.
Wheels/Tires: One of the car's best features is its set of reproduction 15-inch Keystone Klassic wheels, which look period-perfect. They're wrapped with 215/60R15 Firestone tires in front and 235/60R15 Goodyear rubber in the rear.
Paint/Body: Eagle-eye Mopar fans will notice the owner had the Duster's original taillight panel replaced with the sleeker-looking panel from a Dodge Demon—a subtle but labor-intensive modification. The side-marker lights were shaved, too, while the chrome bumpers were painted black—along with the hood and Mopar Performance hoodscoop. And that bitchin' rear spoiler? It's a super-rare Mopar piece originally offered in the Direct Connection catalog more than 30 years ago. The Winning Collection, in Asheville, NC, did much of the bodywork, including changing the car's original drab brown color to bright red.
Interior: It's pretty much stock black vinyl, except for a custom gauge cluster insert with a full complement of Auto Meter instruments. Just Dashes also created the custom dashpad that incorporates a nicely integrated gauge pod. It's filled with an air/fuel meter, fuel-pressure gauge, and boost gauge.
5/12
Fortunately, owner Brian Mimken wasn't mumbling to
himself or gesturing wildly when we caught up with him. He wasn't
adjusting a tinfoil hat, either, and his wife even let him wear shoes
with laces for our photo shoot. All in all, he seemed perfectly normal.
Then again, how normal is it to channel one's energy into a hair-dried
Slant Six? Just to be safe, we kept our arms low, in a non-threatening
manner, and didn't mention a word about those satellites watching our
every move.
Brian says the vision for building the car didn't come from the
voices in his head, but the experiences of fellow Slant Six nut
jobs—enthusiasts who built dual-purpose street/strip cars. So he went
out and found a $500 project car that, in his words, barely ran or
stopped. It was a start.
2/12
"The Slant Six is a great engine, and I wanted to
keep the six in the car," he says. "I also wanted to do something other
than just swapping in a V8. That's been done before, and an intercooled
turbo system seemed like a great way to make a statement."
Although we're not qualified or licensed to stamp "sane" on Brian's
papers, we have to admit that pressurizing the 225ci Slant Six isn't
necessarily the craziest idea we've ever heard. It was never an outright
powerhouse in regular-production form, but the 30-degree slant of its
cylinder case—designed to enable a lower hood line in Chrysler's
original compact cars—enabled uncompromised intake and exhaust systems.
In fact, the manifolds' bends had large radii with no airflow-killing
corners, and the intake and exhaust tubes were nearly equal in length.
That ensured excellent, equalized mixture delivery to the combustion
chambers and basically tuned exhaust. Not bad for an entry-level engine.
3/12
"Make no mistake, the plumbing and routing wasn't
easy," he says. "There's no kit, so it was something we just had to
figure out by trial and error."
The exhaust tubing had to be reconfigured several times during the
build due to inadequate planning for things such as the driveshaft loop
and the need to relocate the intercooler and turbocharger more than
once. Brian also had to run oil supply and return lines for the turbo,
using braided stainless hoses for durability. There were front-end mods
to support the intercooler system, too, and countless hours were spent
on a chassis dyno to nail the tuning and ignition system. After all, who
do you call about the intricacies of a blow-through turbo system on a
Slant Six?
4/12
"I knew from the very start it wasn't going to be
the fastest car at the track, but that wasn't the point," he says.
"Building something original and seeing my idea through to completion
was. This car gets tons of attention, and it's a blast to drive. There's
a real kick to the turbo system, too, and I can take nearly 15 psi with
minor changes. It's fun in every sense of the word."
Insanity and inspiration are simply different sides of the same coin.
Building a 1974 Slant Six–powered Duster may not seem rational to many,
but everyone reading this understands that another car guy's affinity
for certain cars and engines has little to do with logic and everything
to do with emotion. Instead of a conventional V8 'Cuda, this guy built a
turbo Slant Six. In that regard, Brian Mimken might just be crazy. Tech Notes
Who: Brian Mimken
What: 1974 Plymouth Duster—aka "Sixy Beast"
Where: Etowah, NC
Engine: The original tried-and-true, 225ci Slant Six features 0.030-over pistons, a stock forged crankshaft and stock rods. Compression is kept to a boost-friendly 8.4:1, and the stock cylinder head was treated to a three-angle valve job and fitted with 1.70/1.44-inch stainless valves. The camshaft is a Mopar Performance "244" stick, with 244 degrees of duration and 0.436/0.436-inch lift. Squires Turbo Systems supplied the GT35 turbocharger, which is mounted behind the rear axle and blows about 7 pounds of boost through a Holley 390-cfm 4-bbl, modified for forced induction, into an Offenhauser aluminum intake manifold. A pair of Clifford Slant Six shorty exhaust headers feeds a 2.5-inch flow tube to the turbo, with exhaust routed to a 3-inch outlet. An air-to-air intercooler adapted from a late-model Nissan 350Z helps cool the intake charge. The engine also uses the stock distributor, along with an upgraded coil and a timing retard controller. All told, the turbocharged tower of power produces 250 hp and 330 lb-ft of torque. Don't snicker—that's a 240 percent increase in horsepower and a nearly 185 percent jump in torque over the stock 105hp/180–lb-ft output.
Transmission: The stock slushbox probably wouldn't have been capable of handling the high-pressure Slant Six, so Cope Racing Transmission built a street/strip version of the A904 three-speed automatic and fitted it with a 2,500-stall PTC torque converter, which helps the Duster get off the line quickly.
Rearend: Nothing trick here—just proven, durable components, including a Mopar 83⁄4-inch axle fitted with a Sure Grip limited-slip differential and 3.23 gears.
Suspension: Who knew Hotchkis made handling parts for Dusters? This car's got 'em, including front adjustable upper control arms and a thick, 1.25-inch sway bar. There's also QA1 shocks up front, along with the stock torsion bars. In the rear, it's the stock leaf springs, QA1 shocks, and a Hotchkis 1-inch sway bar.
Brakes: Factory-style 11-inch disc brakes up front and simple 10-inch drums in the rear.
Wheels/Tires: One of the car's best features is its set of reproduction 15-inch Keystone Klassic wheels, which look period-perfect. They're wrapped with 215/60R15 Firestone tires in front and 235/60R15 Goodyear rubber in the rear.
Paint/Body: Eagle-eye Mopar fans will notice the owner had the Duster's original taillight panel replaced with the sleeker-looking panel from a Dodge Demon—a subtle but labor-intensive modification. The side-marker lights were shaved, too, while the chrome bumpers were painted black—along with the hood and Mopar Performance hoodscoop. And that bitchin' rear spoiler? It's a super-rare Mopar piece originally offered in the Direct Connection catalog more than 30 years ago. The Winning Collection, in Asheville, NC, did much of the bodywork, including changing the car's original drab brown color to bright red.
Interior: It's pretty much stock black vinyl, except for a custom gauge cluster insert with a full complement of Auto Meter instruments. Just Dashes also created the custom dashpad that incorporates a nicely integrated gauge pod. It's filled with an air/fuel meter, fuel-pressure gauge, and boost gauge.
5/12
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