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February 2005 Willies Workbench Holley Carburetors

Posted in How To: Tech Qa on February 1, 2005
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Fuel injection is undoubtedly the hands-down winner when it comes to off-highway driveability and fuel mileage. However, the carburetor is far from dead. While I own two fuel-injected 4x4s, my main play toy uses a carburetor. There are several reasons for this, but mainly just one word describes it: simplicity. No computer, no wiring, no sensors. Just a mechanical connection between the carburetor and my foot.

I've tried a lot of different carburetors over the years, some of them good, some of them not so good, and only two that I could call really excellent. One of the excellent ones is Holley's Truck Avenger.

Holley carburetors have been around since Henry Ford built his Model Ts and have been used on just about every internal-combustion engine built, and in cars, trucks, tanks, aircraft, racecars and yes, four-wheelers.

Holleys have always been a favorite with the hands-on guy who likes to modify things. That's because of their design simplicity and because of the interchangeability of parts from one model to another within a given series. Still, up to now there never has been an out-of-the-box-bolt-it-on-let's-go-'wheeling Holley carb. You needed to add a special needle and seat, modify the vent tubes, modify the power valve feed to prevent blow out, and perhaps lower the float level.

This is all changed with the Truck Avenger. Available in 670- and 770-cfm models, they are truly in most instances an out-of-the-box-bolt-it-on-let's-go-'wheeling carb. Holley did its homework on this one and added special vent tubes, blow-out protection for the power valve, and a redesigned fuel-metering system that prevents fuel spillover through the boosters at extreme angles. Due to the unique vacuum signal my engine produces, I did make a couple of jet changes and an accelerator pump-cam change to get optimum performance. And performance I did get.

Holley claims this carb will maintain an idle at a 45-degree incline. They're wrong. It will go even more, and this is downhill as well as uphill, and even on sidehills.

Besides its four-wheeling driveability, what makes this carburetor so great is what's made Holleys so great in the past. It's simple and easy to work on.

Something I did immediately notice when making a jet change was that Holley no longer uses those hard-to-fit O-rings on the fuel crossover tube. These have been replaced with easy-to-install, positive-sealing conical sleeves.

The only area in which we could find fault with this carb involved its fuel mileage. After running it for a year, the fuel mileage figures came in at just under 2 mpg of what we had been getting with our old spread-bore carb.

If you're looking for a replacement carb or something for that newly built engine, and don't want to deal with complexity of fuel injection, by all means, take a look at Holley's Truck Avenger.

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