On the advice of Phil at Custom Rebuilt Carburetors, here in New Joysey, who I bought the 7042273 Quadrajet from in 2005, I unbolted it and brought it by his shop where he freshened it up. He ended up putting in a pair of BE secondary metering rods, replacing the leaner stock CR rods and rechecking everything on the flow bench.
No flat spot anymore. A noticeably more linear power band.
Runs scary fast now - keeps pulling all the way up the rpm range. Thankfully I have forged connecting rods now. [img]<<GRAEMLIN_URL>>/burnout.gif[/img]
Here's Phil's website. Lots of neat stuff vintage stuff there. He has a lot of rare carbs in case anyone is looking for something weird and original.
http://customrebuiltcarbs.com/