[jhirasak]

A method to fill the extra progression hole that does not require heat would be to use some epoxy like JB Weld. Before you fill the hole that you want to eliminate, you should put a polyethylene liner inside the throat to keep the epoxy from leaking into the barrel. After the epoxy has hardened, check and make sure that the epoxy is level with the inside of the barrel and then you can have the carb drilled for the progression hole to match the three other carbs. I noticed another thread by Bill Culbertson that had some details on how the drilling could be accomplished.