Guys - I'd like to jump in here and ask for help but first I will suggest all you Rochester Carb lovers/haters go to
www.tocmp.com/manuals/Carbs and there you will find a wealth of Service Bulletins on these and other carbs. Bulletin 9D-8 explains the hole in the bottom of the carb is part of a "vacume operated power System included in the carb to provide additional fuel for sustained high speed driving or increased road load power." The details of how this works is explained in detail. I have run my 235 w/ Rochester BC both plugged (the way I bought it) and unplugged as I rebuilt it and I have never noticed a difference in performance.
Over the last couple of months I have rebuilt and had one professional rebuild done on a Roch. Mdl BC carb with auto choke and I am now 99.9% sure the carb is correct. I can set float levels blindfolded. All parts are new and correct. But, I can't stop the carb from leaking excessivly. On start up it runs dry until the bowl level fills at which point it leaks out the pump plunger lever and if allowed to continue running it will leak out a small vent hole in the top of the carb. This leak "pulses" which is the fuel pump working. Is it possible for the fuel pump to overpower the float and open the needle valve and cause this condition? I obviously don't observe the problem long enough for the truck to explode, I am certain the needle valve is closing properly when the carb is installed on the truck. I appreciate any thoughts on this problem.
