Originally posted by lluciano77
That is a new description they added recently. I have a few older Holley books in my bookshelf and none of them recommend 390s for 2x4s.
I have used two 450s, two 600s, and two 750s. The 600s were about right for my 5.0.. The 750s were a bit too much. When I used the 450s, the mixture was lean all around. The idle circuit was insufficient, and the top end (PVCR area) was inadequate.
That's the very reason my next carb purchase will be a Race Demon RS. Adjustable everything. No tiny drills or impossibly small chunks of brass needed. One carb does it all.
This was all so simple when I didn't give a hoot about the last hundredth of a second.