Panic has a point. I have used only chassis dyno's, mainly because I'm too lazy to pull an engine just to have to put it back in. Things as minor as a tire pressure adjustment or how tightly you pull the straps down can affect your readings from run to run. However, mostly I use the dyno to check the AFR's and make sure the ignition system is up to snuff. In my opinion good recordkeeping with lots of runs at the track looking at mph are the best indicator of hp.
