As already mentioned they can be a valueable tuning aid but can also be hard on parts. I am like you and prefer an engine dyno on a new piece but not on rebuild, unless it's free!

After 3 unsuccessful trips to the track I finally put the Dart on chassis dyno when I first put it together. It would drive around and idle fine but would die in the water box

During a pull on the chassis dyno to figure out the constant flow mechanical injection I could see enough flames to cook a hot dog inside the injection hat
So we pulled the heads off to find the material between #2 and #4 was not there! Fixed that and severe valve float and the rest is history!!
I don't like the engine braking with that #2k drum driving the tires, pretty hard on parts.

check the video

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