..what size carb

Just to set the stage. I have a 289 bored out 30 over. Edelbrock Performer heads,Edelbrock 4 barrel intake, mild hydraulic cam,roller rockers, windage tray, Edelbrock high flow water pump and electric fan. So what carb? I live in Canada ...about 3440 feet above sea level. I happen to have a holley 570 Avenger I got for a song at a garage sale but I'm thinkin maybe its not enough... so I'm interested to see what you all think...Thanks

It would be helpful to know what vehicle it is in and how heavy,gearing trans type(and mods if its an auto).Also which intake are you running?..I would say a 600-650 cfm at sea level depending on usage...Since you already have the avenger throw it on and see how it works...I'm not sure how altitude affects carb sizing..Maybe you need a larger than normal carb with the thinner air?

I run a 650 DP holley on my 67 mustang, with a very simular engine. It works great. I have 3.80 rear gears, so that makes the DP very streetable.

Its going in a 68 Mustang, intake is a Edelbrock Performer, trans is a C4 with a B&M shift kit installed, just for kicks in trying to anticipate this question the rear end is the old tried and true 2:79 this will be rectified when the budget allows. I don't know if altitude affects carb size either, I do know it plays a factor in how the carb is jetted.BTW FRDNUT ..my car came from the factory looking just like yours minus the GT wheels

The 570 is plenty of carb for your use. Unless you wind it to 8000, you don't have enough air demand to use anything bigger.

CKelly is right, the 570 is fine for your application. You may need to drop down two jet sizes at your altitude. The rule of thumb is one size for every 2000 feet of altitude over sea level.

Thanks to all for the sound advice, I will go with the Avenger for now and yes I agree the jets need to be changed. This has been a 6 year resto from the ground up so I am pumped to hit the road ...hopefully this year