I am trying to Choose a Carb for a 400 CU smallblock chevy. It has a 650 double pumper right now and sucks to much gas and bogs, has bad throtle response.
The engine has 2.02- 1.60 valve 64cc heads, RPM intake, 280 cam, auto trans, in a Camaro.
Would a 750 Vacume secondary be to big or just right. I was looking at Both Holly street avenger and Demon 750's.
Thanks, in advance for help...
N. M.  

I imagine that is not the 650 carb's fault but yet the fault of the fuel side of that carb or some other engine problem. If you don't have the confidence to try to troubleshoot you could try a different carb though...

Hey Mike,I just might be able to help.I built a 412 about 15 years ago,wasn't much for gas milage,but was a blast to drive.It had flat top pistons and 76cc heads,with small valves.Stock crank and 5.56 rods.Cam was made by Perfict Circle;it had .480 lift and 230 duration@.050.110 lobe seperation and 106 intake centerline. Performer intake and 650 vac.secondary.1-5/8 primary tube headers with 3 in.collectors and 2-1/4 exhaust.I ran a turbo 400 with a 1800-2200 stall and 3.42 gears.It carried a 4000 lb.SILVERADO to 70 mph.trap speeds in an eigth mile,with very bad tire spin.

I had the carb set at this.2000 ft, altitude.

72 jets,31 squirters,secondary throttle opend one and one half turns.Be sure not to uncover the fuel transfer slot!Also make sure the low speed and high speed air tubes are clean.The air tubes are located just in front of the boosters.Look inside the choke horn if you have one.You can clean them by removing the distribution block and spraying carb.cleaner in each hole.HOLLEYS ARE BAD FOR GETTING THE AIR BLEEDS CLOGED! Wear safety glasses!!!!!!!!!!!!