I have never rebuilt a carb before and have not seen to many apart. I bought a 650 DP and a pro form main body both off ebay, and on the throttle plate on the 650 there are the grooves that go from the little holes by the butterflies to the onthe ones on the other side. Please tell me what they are called so I do not keep calling them grooves. Well the question is why would someone either weld or put JB weld in the middle of those grooves then sand it flat. Is this a performance trick or an idiot who just cost me a throttle plate.

thank you

Jacy

jacy

it sounds as if someone converted(or tried to) that baseplate for use with a 4 corner idle circuit. all of the mods described must be done otherwise the idle circuit won't function correctly. you will also need a secondary metering block with idle mixture screws.

installation of a secondary idle circuit involves several machine operations, some of which differ with the part number of the carb being modified. common modifications include pluggine the constant idle feed discarge holes in the throttle body and drilling a .090-inch replacement fuel outlet hole in each secondary throttle bore. these holes should be located in the same relative location as the primary curb idle discharge outlets. the secondary idle air bleeds will also have to be enlarged to the same diameter as the primary bleeds.

in order to have the secondary idle circuit function as desired, it is necessary to totally seperate it from the counterpart circuit on the primary side. a fuel transfer track machined in the top of the throttle body connects both circuits. it must be plugged. this may be accomplished with epoxy or small hole may be drilled and an appropriately sized steel plug pressed into place. some carbs (late model 850's) may have this track plugged. info taken from Holley Carburetors By Dave Emanuel.

if by chance the constant feed discharge holes are NOT plugged and new idle feed holes WERE NOT drilled, it may be possible for you to unblock the idle transfer tracks and have the carb function correctly without 4 corner idle.