Superchargers and pilots seem to go hand-in-hand. After all, blowers made it possible for WWII planes to fly higher and faster than ever before. So it's only fitting that David Payte, who used to fly F-4 Phantoms off a carrier deck, and now pulls the joystick on a supercharged, 800hp T-28 Trojan, would want one on his '62 Corvette.
Not just any supercharger, though. His 451 Roots-style unit was originally designed by none other than Zora Duntov and John Dolza. (The latter was the engineer also known for developing the first fuel-injection system on a '57 Corvette, which made the 283hp, 283cid small-block the first production engine in the world to boast 1 hp per cubic inch). However, it was GM engineers John Camden and Lou Cuttitta who made this feisty air pump work on an actual car back in the late '50s. Apparently five prototypes were built, and only two were ever installed on cars for testing.
Payte discovered this nugget of information in Kenneth Kayser's lengthily titled book, The History of GM's Ramjet Fuel Injection on the Chevrolet V-8 and its Corvette Racing Pedigree. As a favor, he gave a copy to his mechanic, Larry Hofer of The Corvette Shop in San Diego, who became fascinated with the idea of putting together a running version of this little-known supercharger. How come?
"Oh, I like weird s---," he admits. "We do a lot of cool custom stuff [at our shop], such as a 496 big-block in a '99 Corvette, and a 502 in an '86." (The latter appeared on the cover of the July '98 issue of VETTE.)
Problem was, there wasn't much information regarding this unit and very few pictures. Even so, after several hours of research, Hofer called Payte and convinced him he could pull about 500 horses out of his 383 stroker engine by using this little pump, and create an utterly distinctive look as well.
Payte had some reservations; since he was already pretty happy with the way his Vette was running with a manual fuel-injection setup and Edelbrock aluminum heads. He was also a little skeptical that Hofer could even find one of the Duntov units, much less get it to run. After much debate Payte gave in, but he insisted that Hofer keep his original-style Rochester factory setup intact in case they had to put it back on the car.
Hofer was excited to tackle the project, but knew he was going to face many challenges, and would have to do some digging. Even though none of these unobtanium blowers were actually in service, he discovered one in a Corvette parts collection owned by Dave Crane in Riverside, California. Interestingly enough, before Kayser's book came out, nobody realized what this Rocketeer-style device was, and it was nearly parted out.
According to Hofer, the 451 supercharger was installed in the '50s on trucks, tractors, and boats, and is an earlier version of the better-known 453 blower used on Detroit diesels. After getting a closer look at this antique jewel, reminiscent of Flash Gordon-type, "futuristic technology" seen in old science-fiction movies, Hofer set to work on obtaining all the right stuff. He started by contacting John Marquardt of John's Fuel Injection in Paramount, California, who has been collecting Corvette fuel-injection parts for more than 30 years and actually knew about the 451 project. He even had some of the impossible-to-find parts, such as a four-nozzle splitter (called a "spider"), mounted upstream of the blower. Without this key component, Hofer would have had to cut down an eight-nozzle unit and re-weld it to get things to fit.
As Hofer began collecting parts and doing research, it became clear that one of the biggest hurdles was going to be the fuel-management system, since there was no computer in the car.
"The air meter on a Rochester fuel injection is based on airflow," Hofer explains. "As long as you have the fuel curve accurate, it does a pretty good job of injecting the fuel in the right amounts. A venturi at the air intake detects pressure drop, indicating more airflow. It's similar to a venturi in a carburetor."
The real problem was actually going from eight to four fuel injectors. Hofer had smaller ones with bigger holes (0.024 vs. 0.011 inches) custom-made by Jim Thorpe in Iowa, who specializes in injector-orifice plates. "An enrichment diaphragm measures the density of air in inches of vacuum," Hofer adds. "It's load sensitive in order to enrich the fuel mixture."
Since some of these components date back to the Eisenhower era, long before the advent of electronic controls, consistency was an issue. "The biggest back-and-forth on the project was the refinement on the fuel meter," Hofer recalls. "The same ones all seem to meter a little bit differently, so we had to use trial-and-error, as described in Kayser's book."
He tried out three different meters in all and ended up combining parts from two of them. An oxygen sensor and a boost gauge were used for testing as well (and later installed permanently) to sort everything out. Eventually, Hofer determined that the 11:1 air/fuel ratio was too fat for driving and fouled the plugs, so he settled on a 14 to 15:1 ratio for typical street driving.
"It's surprising how much the oxygen sensor's readings move around," Hofer observes. "Mechanical injection is just not as precise as electronic. I expected it to be more stable." Fortunately, the standard ignition worked OK, so he didn't have to change the look of the engine bay for a hotter spark.
With the blower set at 5 to 6 pounds of boost, Payte estimates around 500 horses, about a 100 hp gain on the 9:1 383 stroker motor. Even better, "It's the only operating Duntov C1 blower in the world," he claims, and as far as we know, he's right. "People stop and marvel at it for half an hour, wondering what it is." (Readers who have any further information are invited to contact Hofer at The Corvette Shop.)
While the engine is dressed in distinctive vintage duds, the rest of the car benefits from coilovers in the front, Wilwood 12-inch disc brakes (way better than those old drums!), a Tremec five-speed, heavy-duty leaf springs, and a Currie Ford 9-inch loaded with 3.25:1 gears-all the better to handle the healthy increase in power that Duntov and his engineers envisioned.
"We're still trying to get as much horse-power as possible," Payte notes, looking fit in his "Right Stuff" flight jacket. Would you expect anything else from a fighter pilot?