AED Carburetor Spacers offer many distinct advantages that are worth mentioning. Besides traditional tuning changes in plenum volume which can improve torque and power output, Birchwood is a great thermal barrier. By keeping fuel bowls cool you get a noticeable increase in fuel density, resulting in a better charge available for combustion. Results on the dyno of up to 20 horsepower. AED originally designed these spacers for racing but soon found out the benefits on street cars eliminating hot soak and vapor lock problems associated with high underhood temperatures. Todays fuels have significantly lower boiling points compounding these problems especially with aluminum manifolds. They are coated with a special sealer to promote sealing and give a great look.Pit Stop USA offers AED 1/2" Birchwood Carburetor Spacer - Standard Holley 6150 at low everyday prices. Be sure to check out all of our products from AED - Advanced Engine Design including AED Carburetor Spacers.