Well, I went to a test n tune at a local track last night. My goal was to fine tune my A/F ratio on my 600 Holley. I really don't know much about carb tuning at all, but based on what others have mentioned on this forum, I was basically taking my stock out-of-the-box settings, and then backing the screws out about a half turn for each pass, and then recording my MPH. My thought was that I might see an increase in MPH, and then to keep tuning from there, until I saw a decrease, and then to leave it at that point where the MPH was highest. Anyway, it just seems like I did not see any changes in my MPH, despite adjusting the screws both in and out at least 2 full turns each way. Is the 1/8 mile just not a good way to tune my A/F ratio?? Would I see the effects better in 1/4 mile?? I went to the 1/8 mile track because it is 10 mins from my house (1/4 mile track is 1 hr away :mad: ).
Anyway, this is a stock 1850 Holley, 600 cfm, no jet changes, etc.
Thoughts?

The screws are the idle mixture adjustment and will have little effect on your elapsed time unless they are way out of whack. Your A/F ratio in the power mode is mainly controlled by the jets and power valve channel restrictors.

The screws only change the idle mixture. You need to pull the fuel bowls and change jets to change the above idle mixture.

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So the real test is to change the jets, as well as look at the plugs, and play with the timing. Correct?

I like to go up in jets first. That way you don't inadvertently lean the engine out. If the car slows down, go the other direction. Keep going, in whichever direction the car speeds up, until the car slows down. Then go back to the fastest jets. Look at the mph and not the ET. The ET will follow. Do the same with timing changes, look at the MPH. MPH is much more consistant than ET. ET is heavily influenced by traction, much more so than mph. Note, too, that the weather will have a noticable influence on mph, so take that into consideration.