Carburetor spacers and heat insulators come in various designs and materials, each serving a specific purpose. The most common types are 4-hole, divided wall, and open spacers, available in aluminum, wood fiber laminate, plastic, or rubber gasket material. Choosing the right one depends on your intended use.

These spacers are used primarily for two reasons:

1. Adjusting the engine’s power band to optimize performance.
2. Preventing heat-related issues like vapor lock.

Do You Experience Vapor Lock or Hard Starts at Operating Temperature?

If your engine struggles with fuel boiling in the carburetor (vapor lock) or is hard to restart when hot, follow these steps:

• First, check your cooling system’s efficiency.
• Ensure fuel lines and components aren’t too close to heat sources.
• If the issue persists, a heat insulator or spacer may help.

Choosing the Right Heat Insulator

A heat insulator is a thick rubber gasket that prevents heat transfer to the carburetor. These insulators come with longer studs and are made of gasket material, so no extra gaskets are needed for installation.

For more severe heat issues, a spacer made of wood fiber laminate or plastic is recommended. The 4-hole spacer is the most effective heat blocker among them.

Want to Adjust Your Engine’s Power Band?

A spacer can help fine-tune your engine’s performance. The most common types are:

• 4-Hole Spacer – Best for street performance engines with a dual-plane intake. It enhances low-end torque and throttle response, shifting the power band to lower RPMs.
• Divided Wall Spacer – Provides extra plenum intake volume, improving high-RPM performance and extending the power band into the higher revs.

When to Use an Open Spacer

Open spacers are designed only for single-plane intakes. They increase airflow and plenum volume, improving top-end performance. However, they are not recommended for dual-plane intakes, as they can reduce low-end power and throttle response.

Which Material Should You Use?

The choice of material affects heat transfer and durability, but not the spacer’s performance effect.

Note: For racing and competition, regulations often allow only aluminum spacers.

Conclusion

If you need to reduce heat transfer, choose a heat insulator or a wood/plastic spacer. For performance tuning, use a 4-hole, divided wall, or open spacer, depending on your intake type and desired power band adjustments.