Instead of replacing the original...
Instead of replacing the original metering blocks, Willy's installed a pair of its own adjustable units.
One trick addition to our Holley was the addition of Willy's own externally adjustable metering blocks so there is no longer any concern about fuel spillage or torn gaskets should a jet adjustment be necessary. Krup says, "The factory Holley metering block is about as straight as your leg is. You're using four corner points to pull the thing snug and seal the thing all the way across. So the body isn't straight; the metering block isn't straight. The metering blocks we put in there are 100-percent flat except for the accelerator pump which is 0.004-inch higher because it's a pressurized port. The raised surface makes it crush the gasket even tighter in there so all the surfaces stay sealed up 100 percent."
The final product is ready...
The final product is ready for bench adjustments and another run on the dyno mule for fine-tuning all the circuits.
Willy's metering blocks also feature replaceable metering valves. Each "click" on the adjusting screws provides a two-jet number change richer or leaner. There are six different valves to choose from, providing primary or secondary jetting equivalents ranging from 60 to 68 all the way up to 90 to 98. Our carb was fitted with a pair of blocks providing jetting adjustments from 70 to 78, as well as a pair of jet extensions and a slotted float on the secondary side to ensure the engine gets plenty of fuel during hard launches.
Our carb's throttle plates were additionally drilled with extra air holes so the unit will now idle on an engine with a big, lumpy cam without burning your eyes. Krup says, "It ought to sit there and just thump along right at 900 rpm."
The newly rebuilt Holley struts...
The newly rebuilt Holley struts its stuff on the dyno after bench adjustments and fine-tuning. The results were well worth the effort.
Since Willy's dyno-tests each carb that comes into the shop when it arrives, it's no surprise that each completed carb goes back onto the dyno for tuning and evaluation after receiving a makeover.
Our results? How about 20 lb-ft of torque and about 24 hp. "We feel like we get the carburetor as close as we can without having to be right there with the customer," Krup says. "Very few carburetor shops go through the added time to run them after they've been worked on. Running them on the dyno afterwards and tuning them ensures it will idle and there will be throttle response. it's not going to hesitate and it's going to do everything we possibly have control over. I've seen terrible cases where somebody gets a carburetor back from some place, and its got fuel shooting out the top or the thing flat doesn't idle because some of the circuitry is messed up."