It depends on what the rest of the engine has on it.

 

670 too big.

 

Soarings its a stock 289 for now, the engines in real good shape, clean and strong running but its stock. Eventually like ive said he wants to put in a new cam and heads, what would be an appopriate carb? somewhere around 600cfm? or would that still be too high?

 

A little big still but it will work fine and leaves room to grow without having to buy another carb.

edit- according to the CFM math formula, a 289 running up to 6500 rpm requires a 543 cfm carb.

 

570 street avenger or speed demon, up to a 625 road demon would be good. for him, a 570 would be best. also, a performer rpm or a weiand action plus would be even a better choice.

IMO you cant go wrong with a 598.00 pair of GT40P's. already have stiffer springs and larger valves, plus they are genuine ford castings which gives a more stock appearance and in the long run will hold up better than something aluminum.

 

I'm running a 570cfm on mine, and the only stock parts are the block and crank, and I'm shifting at 6,000rpm with a roller cam. You don't need a big carb to make power. Carb size has little to do with horsepower, it's all about engine displacement, RPM and volumetric efficiency(there's that word again).

 

Hm some good information here, I'll have to make sure he sees this, we are both still learning, i have some basic knowledge (very very basic) about these engines but im learning so thanks guys. So a 570 street avenger carb would be perfect for him with either a performer rpm or weiand action plus manifold, good to know, thanks again guys!