Holley List 4803-1 LS6

[rgalajda]

Restoring a Holley List 4803-1 , 1971 Corvette 454 LS6. This carb is virtually a 3310-1 780 cfm. When I pinned all the orifices Everything was same as a 3310-1 holley except two things.
Primary idle air bleed is .092" / 3310-1 is .078"

Secondary metering block: PVRC .088" / 3310-1 is .068" (Both carbs use a #76 secondary jet)

Those are huge differences. So I am thinking they must have been drilled.
Just wondering if anyone has had any experience with this carb or has pinned one out before?

[rgalajda]

Should have included this picture. Secondary idle air bleed .039" ? ??

[rgalajda]

So this secondary idle air bleed goes into the transfer slot passage. Pictured above. This lower idle air bleed is also found in Quadrajet and other rochester carbs.
First it bleeds air into the vertical fuel supply channel when the idle system is operating, Second , because of its location between the venturi and the throttle blade , the bleed hole is subjected to low pressure , or vacuum , when the throttle blade is opened past the off idle slot and to a point near the lower idle air bleed hole. At this point , the lower idle air bleed becomes a feed to supply fuel to cover up any lag between the off idle fuel system and the start of the main system.
Opening the throttle valves sufficiently increases air velocity through the venturi to cause low pressure at the lower idle air bleeds. As a result , fuel begins to discharge from the lower idle air bleed holes and continues to do so through out part throttle operation to WOT.

Comments are welcome to wether I am looking at this correctly.