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Resurrecting this thread for an update:
Just got back from a 500+ mile road trip. The truck is performing okay, not perfectly by any stretch, but adequately for now. I didn't get a chance to fix the speedo/odo before the trip, so I don't have any good FE numbers (it's fixed now). The best estimate I could make was on the first leg of the trip. I mapquested the distance to the first town we were stopping in, so I filled up before leaving and then filled up there. 12+ mpg, which isn't great, but considering the new engine had only approximately 100 miles on it before the trip, it was still breaking in and so I think that's in line with what's to be expected.
The truck also seems to have good power. At the end of the trip, I finally opened it up (i.e., floored it) on I-70 going up Vail Pass. I was at roughly about 9,000 feet elevation and I'd estimate the grade to be 4-5%. In fourth gear, the truck accelerated up to about 3,300 rpm which corresponds to approximately 75 mph. Not to bad.
The main issue I'm having is that the Q-jet isn't tuned properly, which from my book on Q-jets is a foregone conclusion with the mods I've done, given that the carb rebuild was just all to factory settings. I'm getting exhaust backfire when I let off the throttle at rpms above 2,000, and my lean-rich gauge that runs off an O2 sensor is all over the place at different load-rpm combinations. It seems the consensus is that the Q-jet is about the best street carb out there, when tuned properly, but is also one of the most difficult to tune. I've read through the book once and would probably have to read through it several more times with the carb taken apart and sitting in front of me to really understand how to even begin even fooling with it.
So my plan is to get an Edelbrock Performer 1406 (factory tuned for economy) with an adapter plate for the spread-bore manifold and run it while I delve into the Q-Jet. The Performer/Carter AFB is apparently one of the simplest four-barrel designs and easiest to tune--and it's about the least expensive option out there. I might also get an adjustable distributor vacuum advance canister so I can play with that too.
I guess my one question at this point is whether there's a better carb for me to get in the interim. I like the idea of something different from the Q-jet (as opposed to just finding another Q-jet to try and tune), so I can compare the two and get a better understanding of how various carburetors work. My other option would be a Holley, perhaps, though I haven't looked into the different options there.
Anyhow, thanks for any input/suggestions.
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