340 Vs 360

318willrun said

Sure, it makes sense! See, they are say'n all being equal (same carb, cam, etc), the bigger displacement makes more torque. But if the smaller displacement has the same carb, then it has more because the cubic inches per cfm isn't the same. But if you give the cfm's according to displacement, then all isn't equal because the bigger engine has a bigger carb meaning more opportunity.... Seeeeeeeeee?????????????????

Click to expand...

That's not how it works in practice.

For an extreme example... If you take a 1bbl carb from a slant six and install it on a 440 it will still make more horsepower than the slant six did.

Prepare for more BS guys, When an engine needs to draw more air than the carburetor is rated for, It can and will flow more than CFM rating albeit at a higher pressure drop.

This means that the slant motor might have 1.5" Hg vacuum in the intake manifold at WOT but the 440 might have 4" Hg. the 440 WILL consume more air and make more horsepower, even though it isn't doing it efficiently.

In race engines they typically aim for 0.3" - 0.6" of manifold vacuum, just enough to get the carburetor to meter fuel while allowing for maximum airflow to the engine.

EDIT: this explains why you might see seemingly ridiculously oversized carburetors on smaller capacity engines. low manifold vacuum at WOT = efficiency.