I have a solid axle car and they usually tie around the axle housing in the rear, and round the frame member in the front. They also chock both front tires. Make sure you are pretty well centered on the drum with the rear wheels. Raise the hood to full open and have them put a fan right in front of the grill opening. Make sure the car is warmed up to full operating temp (
oil and water). They should put a sniffer port in one of the pipes, make sure they blow out the condensation on the sniffer so you don't get a bad a/f reading (air to fuel). Once the car is started and in gear, go through the gears to 3rd or 4th pending what rear gears you have. At this point, you should be able to 'cruise' at 2500 rpm and see your a/f around 12:1 - 13:1 ,could be higher or lower at this point pending fuel injection and size of jets on your carb.
Once the pull starts (when you stab the gas pedal) if there is any sort of popping out of the pipes or any a/f above 14:1, let off the gas. If you are 'driving' the car, don't hit the brakes, the drum has it's own brake and will slow the wheels to a stop, best to clutch in and put it in neutral. Dyno's are a great tool determining what changes need to be made to your fuel system, air system and other things that affect performance. For instance, I know that the difference between the typical oval Cobra air cleaner and the K&N Xtreme top air cleaner is about 40 rwhp and 35rwtq. I also know the difference in a carb being jetted to much will rob your car of rwhp, rpm's and driveability.
If it's a good shop, they can tune things out by looking at the air/fuel line. Pay special attention to this and let them tune it, don't try to tune it by ear or by feel. The computerized dyno does not lie. I've dynoed my car probably 12 times over the past 4 years. Changes in air cleaner, rear gears, intake porting and new valve springs have all made huge differences. My first dyno was 356rwhp. The latest 2 weeks ago was 447 rwhp and I spent less than $2,000 for that 91 rwhp.
Good luck! It's fun to see the big numbers, just make sure the numbers you see are the result of a safe tune for a long running engine.
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