Quote Originally Posted by firebird77clone View Post
Using the fancy formula, @4000 rpm and assuming the 80% efficiency yields 289x4000x.8÷3456 = 267.6

That sounds rather small, am I doing something wrong?

The less accurate CIDx2= 578 which is a lot closer to the 650 it was running.

If the Holly 650 was doing it justice before, just get another.
Well, the '73 block suffix 289 is a 454CI engine, and you want to use the maximum rpm, closer to 6000 than 4000. With those numbers and only 0.8 VE yields 630 scfm. Assuming it's better than bone stock, using a VE of 0.85 and 6K rpm pushes to 670scfm. The 650 was probably marginal at the top end.