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How do I choose a carburetor for my Jets?

When the operating altitude of the engine will be 2000 feet higher than your normal altitude, you’ll need to insert a jet one or two sizes smaller than the size currently installed in the carb, which reduces the amount of fuel entering the engine to match the reduced level of oxygen in the air.

How does altitude affect carburetor?

At high elevations, an engine’s performance will decrease, and fuel consumption will increase due to the air being less dense. When the carburetor is modified for high elevation operation, the air-fuel mixture will be too lean for low elevation use.

How to reduce the size of a Holley jet?

Paul, the Holley suggestion of decreasing jet size by one number per 2000′ elevation is a good starting point. You might want to experiment with power valves too.

Where are the Jets located on a Holley jet 2?

Jet 2 The “as delivered” jetting from Holley is very close to optimum for the majority of high performance applications. For the most part, the jets delivered with the carburetor should suffice as your tune-up “baseline”. In a Holley carb, the jets are located in the metering block (behind the fuel bowl).

What’s the metering plate on a Holley 4160?

The proper kit for making this changeover is available from Holley under the part number 34-6. A metering plate is also available from Quick Fuel Technology that allows you to use standard jets on the secondary side of a 4160 (part number 34-2QFT and 34-3QFT).

How are Holley carbs-jets are US calibrated?

1. Out of the box jetting should be close for most applications. 2. Carburetors are calibrated at 70° at sea level. Decrease the jet size, one number for every 2000 ft. increase in altitude. 3. Holley jets are broached, flowed, and stamped according to flow rate. NEVER drill jets, as this seriously alters flow characteristics.