I am by no means a dyno expert - but I have participated in a few sessions from time to time. Do everything the other guys said. I have seen numerous times where repairs are being made on the dyno, where the guy showed up with 87 octane, and were they did not have any kind of plan.
Thats something not yet touched upon. The plan. You should have one. And you should pay for and get enough time to do the job without feeling rushed or like you need to come back again. You need to make two pulls for each variable to establish the direction for any change, and likely a third (or fourth, or more..) to verify the degree of change that delivers the best results. Those places that giev you three pulls are only good for bragging rights - you can't really learn anything meaningful in three pulls.
On a chassis dyno you are generally looking to "fix" two variables - fuel and timing. They are interrelated, and when one changes the other might want to change too.
My tendency is to start off with the timing in a "safe" spot and try to establish a smooth, predictable and reactive fuel curve. What that means is that when you change a jet by two steps the O2 sensor will show that change in the entire curve in a consistant fashion without bouncing lean or rich. This may require float level changes, fuel pressure changes, or on fussy carbs you could end up chasing around with air bleeds. 99 times out of 100 a bone stock Holley will be just fine - - other than being rich. We're not after best peak - or even best average numbers yet - - we just want to get the thing to respond predictably to changes.
Now you have a tuning baseline. Push the timing up and see what happens? Happy? Try more. Sad? Go the other way. You will find a happy spot - - lock things down and go back to fuel. Same drill - - but here you also have that O2 sensor to give you more directional data. Its nice to have - but as long as you don't hear bad things and the meter is not in some crazy 15:1 danger zone (safe ratios are usually in the mid-high 12:1 range) its more important to give the engine what it wants for average power. Peaks don't mean as much as does a nice linear curve. Go back to timing and fine tune/check that now - - your close or there
If you have time/gas/money left - - now is when you can play with other stuff to see "what if" - - pull the air cleaner and make a pull. Open the headers and make a pull. Don't optimize around the tweaked stuff - - use it as directional info for future plans (ie I really need to find a free-er flowing exhaust...).
Above all don't get too stressed out and have fun. Dyno time is cool.
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