Jerry - most home enthusiasts unfortunately do not have the luxury of the 4-gas analyzer.
With the Q-Jets, there are, from memory, three different primary rod profiles (DEFINITELY NOT INTERCHANGABLE) from 1965 to about 1979. There is some documentation of these in the aftermarket. Cliff Ruggles (Mr. Q-Jet) has made a lot of this infomation available from his experience with Q-Jets. There is also a bit of documentation on primary rods (much more on the secondary rods) in the Doug Roe book. I don't know what profiles the newer Q-Jets use, very little documentation that I know of; and I am unaware of any documentation on the Dual-Jets.
I guess it is just a difference in approach. If one has the analyzer and the time, one can physically test; which obviously is the best approach.
But if one does NOT have the analyzer; but being able to pull a sheet on the carburetor in question, and study the metering components allows one to mathematically determine changes that should work.
If one looks at the major automobile carburetor companies since WW-II: Carter, Holley, and Stromberg ALL offered retail aftermarket carburetors. Autolite and Rochester did not do so. If one looks at the documentation available: Carter, Holley (up to about 1960) and Stromberg is great. Holley after 1960 and Rochester is fair, and Autolite is, well, less than fair. To be fair, Rochester's documentation is much better from 1949 to about 1957 than after 1957. Also, Stromberg documentation newer than 1970 is about like that of Rochester.
Jon
