HAHA !! Classic !!
This is one of the oldest questions out there that has several schools of thought, several different perpectives to view them from and all of them with enough credible sources to make them all believable.
Lets start with one of the most radical and the prespective behind it.
Bolt it together and fill it with fluids
Start her up and let her idle a bit
Check the fluids once its got to temp
Rev the bollox off it repeatedly
max revs, under some light or no load to get the rings humming and really bite in as quick as poss. After say 20 miles you should be sorted !!!
This is usually the approach for race engine builders for race only applications whose primary objective is power - its what they would do to an F1 engine and frankly, you cant get much more exotic and delicate than that !!! The reason is they want to get the components worn as quick as poss to prevent excess friction inside which ultimately means it'll probably wear out in no time as nothings had a proper chance to bed in, but it will develop max power for its relatively short life.
The other classic way is as you say, gentle no heavy load driving, not too low or too high revs, and ensuring you dont labour the engine. The idea here is to allow the components the gentlest break in possible and gradually up the ante in small increments to full revs and load to wear things nicely and ensure long engine life. However if you do this too much then you run a real risk of glazing bores, not getting anything to bite properly and end up with an engine that drinks oil like Olly Reed drank pish and is never gonna win power or longevity awards.
One of the more technically plausible ways I was told relates to what the runnnig in process is actually trying to achieve. Basically you want the rings to dig in to the sides of the bores but without excessive in cylinder pressures. This is usually best acheived by creating a vacuum in the cylinder - ie its best to try and run downhill at medium revs the get the rings to key out and be the bores but its not having to do any real positive load and hence not creating larger throttle openings. Obviously the big drawback to this that hills are only so long and you need to have driven up them in the first place. Which concludes that probably the ul;timate way to be the engine in is light accelerative loads on a dyno to get up to speed followed by engine braking through the gears on the dyno to simmulate a gentle downwards slope.
Of course since the morpheine I could have just typed out a really long way to bake a pancake, but hey at least Im trying !!
J.
....I used to be average, now I reminisce !!!
