JM2¢ on Clifford vs. Offenhauser:
The Clifford 42-4501 has larger plenum volume, which means more mass available to any open valve with the same carburetor flow, but also a weaker signal from the intake valve to the venturi at all times (of course, when engine speed is high enough this fades out).
The Clifford also has a larger radius between the front and rear runners to the plenum, which will improve flow at higher speed.
As either engine size or RPM go up, the Clifford will have a bigger power advantage.
I know it's not within the goals of this test (can't do everything - only the ones that would be helpful to most builders), but IMHO where space permits the Clifford might benefit from 1 or 2" spacers between the runners and the ports (of course, this makes it much wider, linkage and fuel line problems, etc.), and also perhaps a 1" spacer under the carburetor (especially a 390, etc.).
The Offy 5416 looks like what they made out of plumbing fixtures in 1940 to add a second carburetor - and before they were willing to admit that the factory manifolds weren't that bad as to contour and design (just too small). The smaller plenum permits leaner jetting and better mileage at low to moderate speeds with no loss of response.
With a small engine at moderate speed (194, stock cam) the power difference will be small.
