I notched it down 3/8". The BBD is the breaking point (bottle neck) of the entire thing. It's a slant six carb when it comes to performing in my opinion. I just tried to give each cylinder access to both barrels for higher RPM (what's that, 4200 rpms? lol) without giving up throttle response.
Maybe get ahold of a carter 2 brl or holley 2brl from a mid 60's 383 car. Not that it would perform better than say ...a holley 390 holley or 500 eddy down low...it def would give some more top end...and or more parts to swap for richer mix.
The thing with the carter 2 brls from these is the lack of rods n jets. I sand papered mine. I remember wayyyyy back when I finally got the power up top... I had mistakenly sanded too much from the rods already and had blackish plugs that never cleaned up. I was 18 and getting vague advice with little explanation as to the why and how...if I had that part I'd have licked it and spread that magic to others to enjoy.
In reality those carter bbd/bbs..er whatever are only 290 cfm...that's a little light on cfm for a powerhouse.lol
