I used this method to break in my mach 427.
The first 3-4 tanks are to flush as much fuel through the engine as possible.
You will get the temps up as you go through more and more tanks.

At wot, the engine was not turning quick enough for the clutch shoes to engage so I left it on the ground with no problems.

At 1 3/4 gallons the engine is just starting to really come alive.

Take your time and follow the steps and you will be rewarded.

This is the easiest time I have ever had breaking in an engine. Thanks Josh for the great tips and procedure.