You can look up the factory as-built specs on any Holley carb at this link:
http://www.holley.com/HiOctn/ProdLine/CarbList.pdf You'll need the "List" number of the carb. On 4-bb's it's stamped into the front of the choke air horn. It's usually a four or five digit number, sometimes with a dash number behind it. And a "0-" to the front and look it up at the above link.
Example, a 4777-2 would be a 0-4777-2 on the list. It shows to be a 650cfm 4150 series double pumper. Note the column that says secondary nozzle size or spring color. A secondary nozzle is a double pumper squirter. A color here denotes which vacuum secondary spring is used. Just thought I'd toss that in for the 4-bbl guys.
This is a very handy tool for those buying used Holley carbs. You can "reset" the carb back to factory sets and start from a known baseline when initially tuning them.
