Replacing a Mikuni Carburetor with a Weber Carburetor

[BJH324JH]

If memory serves right on the dual vacuum advance units used for Federal High Altitude converted vehicles and California emissions trucks the top port is a secondary advance for the "high altitude compensator" that advances the timing by 5 degrees and the bottom one is the main vacuum advance that is used by the carburetor. hope this helps

I will try the lower distributor barb and hope that is the correct one. Thank you btw. If anyone knows for sure if the lower barb on the distributor should be used for the weber, please confirm.