Hi Frank, At idle there will be no vacuum present for the vacuum advance. The vacuum port is located where it will only work when the carburetor is in the "off-idle" and running modes. There will be a very small amount of mechanical advance present at idle...which will increase as the speed increases. Hope this is helpful.


~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end