In our last installment, we assembled an aluminum block Hyper-Pak Slant Six packing 223.3 hp at 5,400 rpm and 280 lb-ft of torque at 3,700. It's got enough suds to run with the V8s and propel any 3,000-pound vehicle through the quarter in the mid-14-second range. This month, we put it to the test in a '62 Valiant and show you how to assemble a platform that will match our results.
We'll be the first to admit that before we built this little motor, we viewed the Slant Six as something to be yanked, making way for a V8 swap. But thanks to Doug Dutra and Clifford Performance, we've been converted. True, if you insist on maximum bang for your buck, build a 360 small-block. But if you want to blaze your own path and draw a crowd every time you pop the hood, build a Hyper-Pak Slant Six. Whether using a rare aluminum block or a common-as-nails iron block, if you follow our recipe, you'll have a car that idles at 900 rpm, runs great in traffic, delivers decent fuel economy, handles well, and blows minds when you mash the gas pedal and the rear skins explode in a cloud of tire smoke. Ladies and gentlemen, the Slant Six has arrived.
First Time Ever Aluminum vs. Iron Slant Six Drag Test
As far as we can tell, nobody's ever done this before. [Ed. note: That's a good enough reason for us to do it]. So, to find out what effect the lightweight block would have on dragstrip performance, we first tested the Valiant with an identically-prepared iron short-block. From its Engle KV-1 cam to its Enginetech cast-aluminum pistons and moly rings, every detail was duplicated for maximum consistency. We even used the same head, induction, headers, fan, and ignition, swapping them between the blocks. The only difference was the iron block's 232ci displacement (thanks to a .060 overbore versus the alloy block's .020 oversize bores and 227-inch measurement). Would the aluminum block's 70-pound weight advantage prove the old saw about every 100 pounds equaling a tenth?
We rolled up to the staging beams at the historic Carlsbad, California, dragstrip, former stomping grounds of Jim Nelson and the aluminum-blocked Dragmaster Dart Slant Six dragster. Tipping the scales at a svelte 3,025 pounds (2,790-pound vehicle weight plus 235-pound driver), the iron Hyper-Pak was ready. Each run was started by brake-torquing the Art Carr converter to maximum stall (2,700) and releasing the brake pedal as the last amber flashed. All upshifts were made by punching the Art Carr full-manual 904 TorqueFlite's buttons at 5,000 rpm. The 24-inch M/T slicks and 3.55 axle ratio put us over the finish line at a perfect 5,000 rpm. The best of several runs was an uncorked 14.695 seconds at 90.98 mph. Wow, our "lowly" Slant Six was turning e.t.'s comparable to a stock Street Hemi.
A few weeks later, we returned with the aluminum block resting under the hood. At 2,955 pounds (2,720-pound vehicle weight plus a still-non-dieting 235-pound driver) we hit the strip several times. Despite a slight jump in top-end numbers, the lighter motor failed to realize any clear-cut advantage. Why? The best we can offer is that a car like the Slant Six A-Body has excellent static and dynamic weight distribution, even with the iron block. Perhaps the reduced mass of the aluminum block is the answer to a question the car isn't asking at this level of performance. But jaws dropped when we yanked the fan belt and ran 14.190 at 94.26, improving the e.t. a full 1/2 second and 3 mph thanks to the elimination of parasitic drag. Many people left the track that day convinced that six really does equal eight.
Weigh Your Options
Our '62 Valiant four-door was originally equipped with an iron-block, 170-cube Slant Six, 904 TorqueFlite, and a tiny 71/4 rear axle. Before the Hyper-Pak transformation, we filled the 13-gallon gas tank, put it on a certified public scale, and saw 2,700 pounds even. Then we yanked the original stuff and installed the aluminum-block Hyper-Pak mill, beefed drivetrain parts, and eliminated unnecessary gee-gaws like the heater and AM radio. After the transformation, we were pleased to find that curb weight (again measured with a full gas tank) grew by a mere 20 pounds to 2,720.
Ritalin Not Required--It's A Hyper-Pak
Now that we've solved the mystery of the aluminum Slant Six, let's take on the equally-mystical Hyper-Pak. With the advent and popularity of the revolutionary new crop of Detroit compact models in 1960, NASCAR invited the automakers to compete in a series of highly-publicized endurance and road races. Ford (Falcon), Chevy (Corvair), and Chrysler (Valiant) took the bait, and each manufacturer quickly whipped up performance-enhancing goodies. Though Ford and Chevy efforts seemed half-hearted, Chrysler engineers really came on strong with a cam, piston, intake, and exhaust package for the Valiant's cast-iron 170-inch low-deck Slant Six (the 225 was not available in Valiants until 1961).
Although NASCAR sponsored several compact-car races through 1961, the two held in conjunction with the '60 Daytona 500 clearly demonstrated the effectiveness of the factory-hopped-up 170 Slant Six. The first was a 10-lap race over a 3.81-mile road course in which Valiants took the top seven spots, with Marvin Panch leading the way with an average speed of 88.134 mph. The second race, a 50-mile charge around the 21/2-mile Daytona tri-oval, opened some eyes. Again, Valiants dominated the top positions, with Panch's Valiant again claiming the victory with an astonishing 123.282-mph average speed. Panch got $1,900 for each win (a total of $3,800 for the day), and the legend of the Slant Six-powered Daytona Valiants was born.
In 1961, many (but not all) of the parts designed for the '60 Daytona Valiants were made available to the general public as a dealer/owner-installed kit for any 170 or 225. Dubbed the Hyper-Pak, it cost $403.30 and carried PN 2205573. Included was a hotter mechanical cam and lifter set (276/268 duration, 0.430 lift); stiffer pushrods; Carter 2951-S AFB four-barrel carburetor; low-profile air cleaner; two-piece cast-iron exhaust headers; high-flow single exhaust with bolt-on chrome tip; revised accelerator linkage; high-capacity clutch and pressure plate; and one of the wildest intake manifolds ever produced by Detroit.
By hanging the carburetor 2 feet away from the cylinder head, the streamlined 15-17-inch-long runners allowed Chrysler engineers (many of whom were members of the Ram Chargers during off hours) to take advantage of the pressure waves that pulse back and forth between the intake valves and carburetor, providing a slight resonant tuning effect at about 4,500 rpm. In essence, when the intake valves open, the incoming fuel air charge enters at a slightly faster rate than that created solely by the falling piston during the intake stroke. The result of this mild form of free supercharging is increased charge density and added power. Chrysler rated the 170 Hyper-Pak at 148 hp (as apposed to 101 hp in stock form) and the 225 Hyper-Pak at 196 hp over 145 stock.
The Hyper-Pak kit was discontinued in 1963 after a few hundred were produced. At over four bills, it cost nearly one quarter the price of a stripped Valiant or Lancer. But Chrysler wasn't concerned with volume; all it needed was for NASCAR to acknowledge the Hyper-Pak as a factory option so it would be legal for racing. Today, the legacy of the factory Hyper-Pak kit lives on in Clifford's repop intake manifold. Then, as now, it never fails to blow minds whenever the hood is lifted.