I read on a website yesterday that weber 40 idfs are 430 cfm each adding up to 860cfm total, is this right?

Seems like a lot for a 1.8...

Each venturi feeds its' own cylinder, so 860/4=215 cfm.

And this is why the 40 idfs, will flow enough air for most 914 engines, as 215 cfm is more air flow than almost all 914 cylinder heads, even when modified....and why the stock or near stock Ventures are suitable for most street engines, keeps the atomization up at low(er) rpm.s.

I told my brother who likes muscle cars about the cfm number and he was like

So I think I should upgrade to 2.0 heat exchangers to get all of that out of the engine as fast as it is going in.

This is something I ran across on a conversion site. 1hp = 1.45 cfm. It may or may not be true but it seems logical to me. I think thats 141 hp per 215 cfm so 4x215 = 560 hp ever seen a 560 hp t4?

V8 guys use 4 IDFs.

141 hp potential from the 40mm venturi feeding each cylinder sounds reasonable- there is a reason 40mm webers run rich and have a low end flat spot on smaller engines. Keep in mind that the conversion is most likely figured out using an open plenum style intake. Our boxer engines are not the average, so any formulas are not based on the setups that we use.

Kevin