Carburetor Spacers and Heat Insulators: Which one do I need?

Carburetor Spacers and Heat Insulators: Which one do I need?
Spacers come in different designs and materials. The most common types of spacers are so-called 4-Hole, divided wall, or open Spacers. They are available in aluminum, wood fiber laminate, plastic, or rubber gasket material. Which one you need depends on what you want to use it for. Spacers are used for various purposes. The 2 main reasons are to adjust the power band of your engine or to prevent heat problems; such as vapor lock.

Is your fuel boiling in the carburetor (Vapor Lock) or is it hard to restart the engine at operating temperature?
First, check the operation of your cooling system and check if fuel lines and components are too close to any heat source. If there is still a heat problem, a heat insulator or spacer can be the solution. The heat insulator is a thick rubber gasket to prevent heat transfer towards the carburetor. The insulators come with longer studs and are made of gasket material, so no extra gaskets needed to install. If the heat problem is more persistent, a spacer of wood fiber laminate or plastic should be used. These are available in different types, but the best heat blocker is the 4-hole variant.

I want to adjust the powerband of my engine, which spacer should I use?
With the help of a spacer, you can certainly improve your performance goal. The most common spacers are 4-hole, divided wall, and open spacers. For a street performance engine with a dual-plane intake, the 4-hole or divided wall can be used. By installing a 4-hole, the low rev response will improve and the powerband will go towards the lower rpm’s. By applying a divided wall you get the opposite result. You provide extra plenum intake volume, which gives you better performance in the high revs and thus increases the power band in higher rpm’s.

When do I use an open spacer?
The open spacers are used on single plane intakes only. If you need more air/plenum intake in your performance motor you can achieve this by using a thick open spacer. We do not recommend the use of open spacers on dual-plane intakes.

What material should I use?
Which material to use depends on the heat transfer and durability. The effect of a spacer is not changed by the material. The heat is best blocked by a wood fiber laminate, then a plastic spacer and aluminum is not a good heat blocker, but is very durable. Sustainability goes the other way: from aluminum, plastic, and wood. 
For many race/competition regulations, only aluminum is often allowed.

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