It's been a while but I've been working on the carb on and off. I've acquired these three holley books which would have been good to have from the start. Each one has good info about the operation of the different circuits in the carb but the one with the blue cover(foreground) is the most current and useful when it comes to suggestions for modification. The one in the background includes a comparison test between the Holley 450 Economaster, Qjet and Rochester 2 barrel on a low performance 350 from the 70's. The Economaster barely edged out the QJ on gas mileage, and had the most torque around 2800 rpms. Too bad they didn't give the exact list number or jetting for the carbs. That would have been helpful!
I got the 2 older books pretty cheap off the internet but the one in the foreground cost about $20 at Barnes and Noble.
Here's an idea that I got from one of the books. Old trick but new to me. Make a carb stand out of 4 carriage bolts and 8 nuts. Really helpful.
Here's another idea that was suggested in the newest book. Since the rebuild kit does not come with a replacement for this spring which controls the power valve, you can shim up the spring using some washers. I have some black plastic ones in place in this photo. Have not tried it yet. More on this later.
Back to the jets for a minute. I bought some jets that turned out to be too big so the car ran rich. I decided to experiment with blocking out part of the area of the jet using a rod, a la Quadrajet. In this case, I measured a bunch of wire things from guitar strings to paperclips and came up with options to emulate a smaller jet. Knowing the diameter of the jet orifice, I measured the diameter of the "rods" and calculated the area of each and subtracted the rod area from the jet area to get the resultant area. Here's a picture of a jet with a wire piece in place. I just screwed the jet back in like this and it works pretty well.
Another use for the guitar strings is to check to see if the passages in the carb are clear. Just run the string in and out, compare depth among different passages and check for residue on the guitar string when you pull it out.
Next experiment is probably going to be about that power valve spring. I have two carbs now so I can just use the top from the second carb and shim up the spring. I think the old worn spring may be causing the power valve to come in late, in other words, activating at a lower vacuum than originally intended and that could account for the whole lean spike in the primaries that I've been puzzled over all along.