Good afternoon, y'all.

Here's one for the carb guys out there that has been bothering the hell out of me:

I rebuilt a first gen 350 - early 70s 2-bolt main w/ flat pistons running around a 9.5:1ish ratio - new internals - i.e. valves, rods, etc. stock heads and intake. I located an early qjet due to the fact that they are supposedly the kings of fuel econ (and the price was right).

The qjet was rebuilt completely, and I do mean completely - new everything. Now... here's the REAL dirt:

I rejetted it for my altitude @5300ft, with rods @ .50 and jets @ .73, the effect being 1 stage leaner for power mode and 2 stages leaner for cruise mode. The secondaries have new rods ("DR" stamp - forget the specs off the top of my head, but this is irrelevant information).

I warmed her up and vacuum gauged it to tune - everything seems to be within spec, and the engine holds a good/steady vacuum reading.

The problem is that I am really feathering the throttle in order to check my fuel econ - to which I have yet to even open the secondaries, and I am coming up with 4 (5 at best) MPG. WTF? I don't quite understand what I'm missing here. Non-spirited driving on an engine that I specced and checked should easily show 10.

I'm blaming something with the qjet, but can't quite put my finger on it.

 

...or I could have a pinhole leak in my rather old and squishy-feeling fuel line. As a matter of fact, I was getting around 6mpg on the old straight 6 with a rebuilt monojet prior to swapping the 350 in.
I would love to use the qjet, but it has its own quirks. I may just replace the fuel line and swap for an edelbrock 1406.