Originally Posted by Nortonfan
Thank you, Cobalt327! My goodness, this is splendid information and I can't thank you enough for sending it along.
This may take me some time to digest and be informed enough to be able to comment and ask relevant questions. As previously mentioned, I have ordered a couple of reference books on this subject and the Ruggles book is one of them.
You are correct in saying that the smaller displacement engine would be easier to adjust to the leaner settings, and I must confess that I had my concerns in this regard; not knowing the range of adjustment one could expect and being able to find a suitable jetting/settings from the larger carburetors while still being able to transition smoothly through the other stages of operation. You have provided plenty information here and opened many doors for me.
I will begin my search for a suitable model Q-jet carburetor from the ones you have suggested to see what comes up, and being that the subject models are not likely candidates as "collectible", will make the affordability issue nothing to be too concerned with.
Again, I'm quite stoked and appreciate this very much!
You are quite welcome. One other attribute of the later style Q-jet casting is that the adjustable part throttle (APT) adjustment is easier to access, located under an aluminum plug in the airhorn. The earlier style carb use an adjustment screw in the baseplate and this often is seized up.
More on this here
. BTW, try to avoid 1975 and early '76 carbs because they are likely to have the aneroid or spool in them, and this complicates tuning.