Holley 2BBL mod
 

My nephew got this Holley 2BBL with the booster mod. Have any of the experts here know anything about it? Nephew told me he put it on the test engine and it runs perfectly.

50 years ago AHRA Super Stock's could run a Holley 2bbl, 650 cfm IIRC. Maybe this a modified version of that carb?? :hmmm:

That looks like a number 6425 Holley 650 cfm two barrel with the choke horn cut off, or it could also be a severely modified 4412 500 cfm carb. I used to run two 6425's on an STR-10 Edelbrock in an IHRA multi carb class. Holley sold three or four inch chromed stacks that fit onto the air horn for even better flow. 6425 is an annular flow carb. Nothing to interupt air flow, since the fuel comes in through the sides of the 'barrels'.

4412 stamped on the metering block.