I need to re-jet my new 650cfm Holley Avenger Carb to deal with the demands of a 350 that has a large cam and 11:1 compression. The overall engine package is almost identical to a '70 LT-1. Does anyone know where to start? I have the specs for the 1970 LT-1 carb (thank you C3VR) but those specs are for a 780cfm carb and GM was known for being slightly over zealous. I'm also going to need different power valves. I'm pretty certain that the stock Holley Avenger specs have this engine running on the lean side, but where should I start??

Contact Holley <www.Holley.com>. Tell them the same thing and they should be able to help.

I totally agree with going to Holley for recommendations. For the power valve sizing, you will need to know how much vacuum you have at idle. Holley has recommendations based on your engine vacuum. You can start with jet size 70s and go from there. My 750 vac secondary came with size 72s and a 6.5 Hg power valve. I reduced my jet size to 70s because the 72s were a little rich. I live in the Houston, TX area. I'm about 12 feet above sea level, with high humidity. The power valve is sized for my engine vacuum at idle which is 15 in. Hg. This is what my motor likes on most days.
You can also buy one of Holley's books. They are a very good guide to help you tune your carb for your application.