required break-in on engines....what's the truth here?>>>>>>
Well unlike my take on the clutch, there is in fact a breakin on engines!
You see there are different sources of friction going on in the engine unlike the clutch.
You have to create a wear pattern in the cam, and this 2000K for 20 minutes is ok, but not really required, that is just a disclaimer for the cam grinders to cover their own butts.
The one thing that needs to be addressed is most importantly dirt in the oil, I dont mean big clumps of oil, but particulates none the less, and if you cdont think it is a real issue, take a sample of your new engine oil build and have it analyzed for particulates and I am quite sure you will be very surprised at what is floating in the oil.
Then there is the ring breakin, and this is the most important issue for an engine breakin. You must run the engine up to temp and maintain the temp/rpm's for a number of hours before the rings are totally seated to the cylinder bores. When I built my engine, I was gettin blow by on my rings, now I have total seal rings and I was not to happy about that. I also noticed I was using a high amount of engine oil.
What I did was to take a nice long 525mile trip to my mom and dads house with the car, just driving normal speeds 75-80 all the way there. My engine oil consumption went down by 50% and that was good. Now when I turn the engine over by hand, even after sitting for a number of weeks I dont hear the blow by anymore. The rings seated and everything is happy.
My take on hard driving/easy driving really is not the issue for me, but running the engine, bringing it up to temp that it will see every time you drive, and maintain that temp and running for a number of hours. That is a good engine breakin for an engine. Make sure the oil is clean, and change it after some running to get all the crap out of the oil. You can be the most cleanest machine shop in the world, but I will guarantee you there is going to be particulates in the oil after any rebuild, and no matter how precision you machine a part, the part that mates to that part will need some running time to find its final operating place.
Dont confuse a clutch with an engine, totally different contact materials. Dont worry about a hard/easy breakin, the engine will do both if built properly, but rather try to fire the engine and run it for as long as possible bringing it up to operating temp the first few thousand miles.
That is my take on the deal, it has worked every time for me.