I understand the concept of normal, "soft" break-in, and it seems to make most sense to me. But in the past, I've heard people suggesting a "hard" break-in. What does this mean? Do you basically just beat the crap out of the engine right away after it is rebuilt? I really don't see how that is good for the engine at all, but some people swear by it. Any input on why it might be beneficial?

 

i've done both...
go with soft.

the only areas a hard breaking is o.k...
when the housings and apex seals are brand new.
AND you dont have the time to break them in, racing and such.
OR you can afford a new motor, in the event of a problem.

When hard break in is used, any little problem like an oil leak, or coolant leak, will multiply the damage done.

for daily drivers, esp turbos, i would always "soft" break in.

 

I swear by the hard break in method but there's more to it than just ragging on it. It also involves changing your oil and filter at mile 20, 500, 1000, and 3000. You actually drive it pretty hard for the first 20 miles. Runs up to redline are just fine. However after the first oil change at mile 20 (or so), you drive it normally, avoiding redlining for the next 1000 miles. It's a bit like a regular breakin period after you drove it hard for 20 miles. Unconventional but works really well. Just remember bearing don't break in. They can't. They don't touch anything but a film of oil. Only your gears and seals break in.

 

would you still recommend this for boosted applications? say a stock fd?