This is what I wanted from my GT350's small-block: intense throttle response with tons of torque and looks that would make Steve McQueen drool. How could I get both with only one modification? The answer was Weber IDA induction.
Of all the engine modifications for increased performance, probably none are as controversial as bolting on a set of 48 IDA Webers.
"Webers are not streetable," I was told. "They load up in traffic and all that carburetion kills your low end." A fellow club member commented, "Those things go out of tune every time the weather changes." I also heard that IDAs have to be synchronized, something akin to black art best left to talented guys with lots of vowels in their last names.
But when forced to confess, each of my advisors had never owned a set of Webers. Could these guys be misinformed? Was it possible the average car nut could learn to live in harmony with downdraft carburetion?
Cobra fanatic Enzo Alibrandi and Jim Inglese, formerly of Inglese Induction Systems, thought so. They thought if I was willing to learn a little about my car and spend some money-lots of money-sprint-car times could be mine. "Once you find your carburetors, do as I say and do not deviate," said Enzo. "It's not rocket science."
Both Alibrandi and Inglese agreed: 48 IDA Webers are the ultimate in adjustable high-performance street carburetion. They can be tuned for low- and high-rpm performance simultaneously. In spite of their exotic looks, IDAs are "only" carburetors: They don't load up any more than your lawn mower's carb as long as proper float levels and jets are used. Going out of tune isn't a problem either, unless someone sticks a screwdriver where it doesn't belong.
Weber carburetors utilize a simple, durable design with few moving parts. There are no rubber diaphragms, metering rods, or plastic seals. The accelerator pump is a brass piston and spring. Also, synchronization is done only once and, with the help of a synchrometer, it can be achieved in 15 minutes by the average enthusiast.
Another plus for these carbs is their independent runner-intake design. Each intake port gets a cool shot of pre-emulsified fuel from its own venturi just a couple of inches away. In fact, it's similar to a good fuel-injection system.
I was sold, so I couldn't make it through another summer without two rows of stacks on my 289. After sifting through foreign-car shops, Hemmings Motor News, eBay, and various club classifieds, I finally located four IDAs for $750 each. At the time, I didn't know how lucky I was. It turns out they haven't been produced for over 15 years so, at times, finding dinosaur eggs can be easier.
Next I had to find an intake. I didn't know going in there were several variations available-none of them inexpensive, of course. I decided to use a newer version with a thermostat housing cast into it like a factory four-barrel intake. It also mounts the Webers back-to-back so all the fuel outlets are on the outside. Unfortunately, most of the Cobra replica builders had the same idea, so I would have to wait six weeks for my back order to arrive from Holman-Moody.
So I was stoked. When could I bolt 'em on? No time soon, it turned out. My carb jets were all wrong, and the chokes (main venturis) were too small. A simple formula-cylinder volume in cc's (cubic inches x 1639 = cc) x peak rpm/2,600-told me I needed approximately 37mm chokes. Unfortunately, mine had been changed to 32mm. A call to Enzo confirmed: "On a 289, 37mm chokes are perfect for going after both ice cream and Corvettes." Luckily, they were available for "only" $28 each, plus I needed idle jets, air correctors, and mains, all at $6 each, times 8. Thank goodness the emulsion tubes were OK. Also, the floats had to be set at the same level. If one was off, all the tuning in the world wouldn't make things right.