I am needing information on the outboard carburetors on my Holley 340 6 bbl set up, list numbers 4789 & 4790. I have been told that the metering plates between the front and rear carburetors are different. However, looking at the 1970 parts book, each metering plate has the same part number listing which to me would indicate they are the same.

Does anyone have the spec information on the front & rear metering plate that will provide the metering jet sizes (PVCR) and the number that is steel stamped into each of the metering plates?

Also, the parts book lists a different part number for the base plate and the diaphragm but they both look identical to me. Does anyone know the difference between the two base plates and diaphragms?

Holley originally delivered the end carburetors with plugs over the idle mixture screws so no one would be tempted to adjust them. Does anyone know how many turns from fully closed those screws were set at from the factory?

Thanks.