Quote Originally Posted by craig akiyama View Post
heat soak not an issue never ran a long time at once air gap manifold
i'm embarrassed to say i don't have a vacuum gauge at the present time
Air gap manifold will not stop heat soak, as heat soak is a condition caused by heat transfer when the motor is turned off. The motor does not have to be run hot to cause heat soak, when the motor is turned off, there is a tremendous amount heat trapped in the metal surrounding the cylinders, aluminum transfers this heat quickly and heat rises. The aluminum heads and manifold are a conduit for heat soak by transferring heat from the motor quickly to the carb. And, the 1-1/2" aluminum spacer can increase heat soak. You can sometimes use a laser thermometer to see a heat soak condition.

BTW, why are you using a 1-1/2" spacer under the carb?

A VACUUM gauge is one of the most inexpensive and valuable tools you'll own...