the engine builder we are using has told us when its built put it in the car drve it about relitivley mildly ( not like a grandad tho) for about 40 mins then bring it down for a rolling road set up. and thrash the bollocks off it. he said when they build race engines they give em a couple of minutes then go go johny bravo. if you need any more time then it aint been built properly. mind you these are race engines and the clearances are greater when cold so as they are at there optimum when being thrashed around a track.

if you get told to run them in for any real length of time they arn't confident in there own work and are just buying time.