Video: Tuning Your Holley Performance Carburetor

Tuning carburetors is an art form, often requiring experienced judgement to determine if and what adjustments need to be made. Holley has been in the carburetor business for over a century, and has mastered this art form. And while the whole process of getting your carb dialed in can be tedious – even a bit daunting – Holley carbs help simplify it by providing great performance straight from the factory. But, depending on where and how you’ll be driving, you may find that some tweaking is necessary.

Obviously, fuel delivery is the name of the game when tuning your carburetor. The whole point is to ensure that the air/fuel ratio and delivery rates are appropriate, providing the best efficiency and performance. The complete process involves a few key steps, as outlined in the video above, provided by Jegs.

The first step, of course, is to set the appropriate fuel level and make adjustments to achieve the proper idle mixture and RPM. After setting this, the intake manifold vacuum reading can be used to select the appropriate power valve.

Once all of this is accomplished, the real fun can begin – re-jetting the carburetor and adjusting its accelerator pump system. It’s in doing these that the tuning process becomes tedious, as the only real way to determine what’s best is through trial-and-error.

This is where a dynamometer would come in handy, allowing testing to be done quickly and concisely. But for those without access to a dyno, tuning can still be done the old-fashioned way by simply driving at each setting and feeling for what works best.

But regardless of the of the testing method, proper jet size is critical to performance. Using the right jets for your application ensures the proper amount of fuel is being delivered at all throttle positions, from idle to wide-open throttle. Nobody wants their engine running rich or lean, as either can cause losses in efficiency, performance, and even harm the engine in the long run.

Equally as crucial as having your carb properly jetted is having the accelerator pump circuit dialed in. The accelerator pump circuit is the most important component of off-idle performance; it primarily performs during hard acceleration and wide-open throttle. And let’s be honest – you didn’t spend all that time and money on your car just to sit at idle.

The accelerator pump circuit is responsible for providing smooth engine-climb when the throttle is quickly opened, and is as important for performance as it is for drivability. So even if you aren’t concerned with lap times and power numbers, it is still one of the most important elements in carburetor tuning.

Fortunately, getting your Holley carb’s accelerator pump circuit set properly is fairly straightforward. As illustrated in the video, it’s important that the clearance between the accelerator pump diaphragm arm and the operating lever is correct. Improper clearance will cause either poor throttle response or premature pump failure.

Along with checking this clearance, there are a number of other adjustments that can be made – such as determining the best nozzle size, diaphragm capacity, or cam profile. All these things will directly affect fuel-delivery during acceleration, and consequently the car’s performance.

Overall, there are a number of factors that will contribute to the amount and type of adjustments that your carburetor will need. But Holley has taken many of these into account, offering great out-of-the-box performance. While some of these adjustments may be necessary, the amount of tweaking you’ll have to do on your Holley carb is minimized – getting your ride out on the road faster than ever.

Be sure to check out the Jegs website for all your performance parts needs, and check out the Jegs YouTube channel for more videos with valuable tech information to help get your vehicle up to speed and performing right.

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About the author

Joshua Phillips

Josh has always been captivated by cars, from legendary classics and late-model American muscle to European supercars.
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