The metering rods are of a step design and are controlled by vacuum and metering rod spring action. At low speeds the metering rod is dropped down into the primary main jets, thus partially closing off the flow of fuel. At higher speeds and less vacuum the rods pull up from the main jets allowing more fuel to flow. Experiment with different springs in order to remove any flat spots, especially if the engine is running any kind of performance camshaft.
1. Which carburetors are these springs compatible with?The S101 spring kit works with Carter AFB and AVS 4-barrel carburetors, as well as some Edelbrock 4-barrel carbs. They install on the metering rod step assembly to control fuel flow.
2. What is included in the S101 spring kit?
This kit contains 10 metering rod springs (two each of five colors): Blue, Yellow, Orange, Pink, and Silver. Use them to tune rod vacuum pull-up and eliminate flat spots or off-idle hesitation.
3. Why are there different colored springs?Each colored spring has a different spring tension (vacuum rating). Swapping to a stiffer or lighter spring adjusts how quickly the metering rod moves, helping optimize mid-range performance and throttle response.
4. How do I choose the right spring for my setup?Start with the Orange spring if you're unsure—it’s the most commonly recommended. Then experiment up or down in tension based on throttle response or suspected flat spots.
5. What does the metering rod spring do?These springs control the vacuum-operated step-up of metering rods, which regulate fuel flow from the primary jets. Proper spring pressure ensures smooth transitions and prevents flat spots under load.
6. Do I need to replace all springs at once?Yes, replace both springs as a pair.
7. Is the S101 kit in stock?Yes, current availability shows as In Stock under the product price. If it's out, you can add your email to the waiting list for restock notifications.
8. How much does shipping cost?Shipping is calculated at checkout based on your location and preferred method. For full rate details, visit our [Shipping Information page].
9. How does this kit compare to others?The S101 features USA-made springs specifically tailored for Carter AFB/AVS and Edelbrock carbs and quality-tested for consistent vacuum ratings—unlike generic spring packs of unknown spec.
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