"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?