Robert,
I build the occasional multi carb setup and recommend checking
the power valves for integrity. Stromberg power valves , even brand new
ones can leak. The PV gasket face in the bowl is a semi frequent source
of leaks as well. Did you actually check the size of the jets with a wire
gage...all too often jets get drilled out....and of course they are never
restamped.
The jetting and PVs are not that far off to deliver only 5 mpg,
providing they are good.
Charlie ny
[email protected]