I picked up a lightly used Holley 390 CFM 8007-0 Carb for my buddies 56 to convert His Teapot as well as changing the Distributor. I have the same Setup on mine.Having a little trouble getting it to Idle in Drive. I had the same problem with mine initially until I got the Transfer Slot adjusted properly. I pulled this One back off Today to check the adjustment of the Throttle Plates in regards to the Transfer Slot. Made a note of how many turns of the screw from not touching the Lever until the correct adjustment for the Slots. I was going to make the secondaries adjustable also by changing the set Screw to something I can turn without taking the Carb back off. This newer Version of this Carb has the adjuster blocked off on top of the Baseplate like Holley doesn't want You to play with it. All the other older Ones have that adjuster open so You can use it. I seem to remember it was Holley who suggested using that Screw to ad a little more air and leave the Primary Speed Screw alone when properly adjusted for Transfer Slots. Has anyone actually used that Secondary adjustment when using One of these Carbs on a stock Motor? I didn't on mine.
I am going to put it back on as is and see if it works better now with the proper adjustment. If I cant get it working properly I guess I will have to drill and Tap the Baseplate. I just wondered if anyone else has had to use that adjuster?