I`ve dynoed all my motors for the last 20 years I wouldn`t have it any other way. I eliminates a lot of guess work and break in before putting the motor in the car. I literally take the motor off the dyno put it in the car and go racing. Because I`ve been using the same engine builder for so many years he has the records of all my builds and dyno pulls. Its cool to try different things and see HP / Torque gains. Example: found a 12 hp gain going from a Strip Dominator to a Victor intake, my small motor liked the 1 7/8 headers I use with my bigger motor over set of 1 5/8 headers, the Super Sucker carb spacer was worth a few hp, my combo didn`t find any gain going from a 750 to a 950 carb. My friend/ mentor works at the shop I use he`s been a Mopar builder/racer for many more years than I`ve even been racing which is 25, he assembles my motors and dynos them and builds my 904s for me on the side.

If you are worried about cost, try to find a good chassis dyno. We went to a local shop and you can have a day for $125/hr. Flywheel HP is nothing unless you can deliver it to the rear tires. Like Jim said, its a tool that can be utilized to find things ahead of time to help you better your ET by utilizing all of the power your making. We dyno'd our car for the first time this year and found that we were running out of the engines power range and found that the timing was out of wack. After the dyno session, we change the timing and went to the track. We picked up a tenth. Its worth it and its good for selecting the proper converter for your car. just my .02 though