The Hudy is pretty good. The only motor you can't break in is a .12 with a rotary unless you can turn another prop button on a lathe. And it's still tough to hook up linkage to the rotary.
But for all other engine with slide carbs this works much better than breaking a motor in while in the car. I recommend one. Also play with the heat gun and tin foil on the head to keep temp. The Hudy's fan really puts off some air over the cooling head and block. Good luck. Chad