AFR lightweight Phenolic carburetor spacers for 4150 style carburetors are available in an 1" thick open or tapered four hole version. Both versions will act as a heat barrier between the manifold and carburetor to keep the fuel in the float bowls cooler, as well as the actual carburetors body itself. This results in a cooler, denser air/fuel induction charge for increasedHP. Our tapered four hole spacer will typically increaseHP and show notable improvements in torque as well. Our open spacer works well in applications requiringmore plenum volume and RPM. Some applications will benefitfrom both installed (tapered and open) assuming you have the hood height to accommodatethem. Both have a clover leaf design making them more efficient by reducing some of the turbulent air directly under the carburetor base. They fit the AFR line of composite intake manifolds perfectly but can be used on most aftermarket manifolds as well.