Originally Posted by Sow&Steady

I do it with the engine in the car and during WOT, I try to build the temp up to about 60 or 70 C for the first 2 tanks. I feel this is rich enough to remove junk, if any, but also warm enough so as start the wearing-in process without prematurely wearing the piston-sleeve.

Next I place the car on the track and drive around rich. Some engines do fine with the same setting that I used in the first part, some will need to be richened a bit more. The idea is still the same, you want to drive it around rich with the throttle almost fully open but at the same time not stalling and not too hot (i.e. around 70 to 80 C at this point). I do this for about 5 to 6 tanks, gradually leaning out each tank so that by the end of the 6th tank on the track, I am running at around 90 C and close to race tune.

Between each of the above tanks, I stop the engine and ensure that the piston is at bottom-dead-center by turning the flywheel and then letting it cool down before doing the next tank.

I feel that this is the best way to heat-cycle and bed-in the engine but of course, there are many opinions on this.