Bottom end rebuild. Break-in procedure?

[KenC]

I had my block honed, clyinders re-ringed, and new crank & rod bearings installed. What's the break-in procedure once I get it put back together and running?

[B318M42W]

Not 100% sure on cars, but on airplanes they use mineral oil for the first 50hrs with an oil change at 25hrs and 50hrs and cautious operation for the break-in. But since you only have bottom end done... mineral oil might not be the best option for you.

[1991 E30 M42]

Drive normally but not a continuous high speeds for the first 500 miles. Occasional quick bursts of speed followed by quick deceleration during this period, is beneficial. Do not take a trip or haul an excessive amount of weight until after 1000 miles. Just use conventional 5w30 for the first 3000 miles, doing your first oil and filter change at 500 miles this is also the time to check cam timing again if you replaced the chain or adjust the valves if you have solid lifters. One thing I like to do but is not normal or required is do another oil change at 1500 then the next at 3000, after that switch to synthetic and change on a regular interval of 3000 miles.

[nickmpower]

I would do an oil change at like 20 miles

[1991 E30 M42]

I would do an oil change at like 20 miles

an oil change that early may cause the rings to not seat properly

[Rich86]

Warm up and drive for 10-15 minutes with decent acceleration and engine braking. Nothing over 4,000 rpms. Stop, let cool and proceed to drive like that a few more times. After 20-30 miles of that sort of driving. Stop and drain oil, replace filter, fill up and drive moderately for another 1500 miles. Avoid highways and constant speeds during this time but feel free to rev it out a little more. Again, you want lots of engine braking. After 1500 miles do the filter and oil again. Continue break in for another 2000-2500 miles then oil and filter one last time before you go to regular interval mile oil changes.

That's pretty much how I broke in my new m10 and it runs great.

You want to seat the rings during this time so some load on the engine is important both accelerating and decellerating.

Avoid lugging the engine during this time as it is very bad for your engine.

After break in. Rev the piss out of it and enjoy!

[quinn11m20]

Screw ALL THAT ! HYPE Dude dog the @#!&*%$#@ out of it.

[doitover]

I would call the manufacturer of your rings or bearings. I don't think break in is that much of an issue these days.

[flyinglizard]

Iuse Rotella truck oil with ZZP, run it about 1-2 hrs, rev it a touch ,no long pulls. Check the compression  and wait for the oil to stop burning off.  Change the oil to a good syn and run it. Use some ZZDP additive of some sort,  for anti scuff.
  Stay off of the clutch  for a while ,( never while cranking).
 I use only "Total Seal  Gapless" rings.They cost more but make power until the rod shoots out.
  Total Seal does not want any oil on the rings upon install. They will not seat. ATF or WD 40 only on the rings.  These break in easy  that way, or never if over oiled.  Many ring manufacturers have a special ring oil or procedure, now days.  
 The TSG rings, keeps the oil cleaner and cooler, and has almost zero leak down for a long time. I have two to three thousand laps on a few of my race engines setup this way.
 PS. some race shops say to warm it up tight, rev it to the race rpm , after a few short burst. Reving the engine , with heat, gets the rings in the same  bore range as the real world/racing revs. This ensures that the rings will "see" the same area of the bore, wi th the same heat/size value. In theory.  I subscribe to it also.

[dvmotorsports]

I don't break in motors. We never did on the race cars. We idled them for a bit to make sure they ran, but once we go to the track, we went WOT. If you want piece of mind, i'd follow either of the above two posts and keep the revs down for at least 500 miles. I put 2 or 3 miles on my stroker before I hammered it, and it's just fine.

[4banger]

ken how much did they have to take the walls down to get the grooves and ring ridges out?

[nicknikolovski]

Break-in - I don't think anyone does that anymore. Just don't exceed 4K rpm for first 1,000km. Then drop the oil and change the filter.

[strypt]

I have tried this method: http://www.mototuneusa.com/break_in_secrets.htm
and I have also tried just a early oil change and then just running it like usual. I can't tell if one engine is running better than the other. Would be interesting to dyno two identical engines (ring gap, bearing play etc etc) and see if there's a measurable difference in that case depending only on break in method.

IMHO: If you are building a standard or even slightly tuned engine, you really can't fail breaking it in. Just don't forget to change oil early

[flyinglizard]

I'll  go with that method. Pretty close to what I do.
  But, I never race with dyno oils. only synthetics. I run the car hard at least an hour before changing oil. I do not let the oiltemp get very high.

[JP 91iS]

Straight from the owners manual:

For the first 1,200 miles drive at varying road and engine speeds. Do not exceed 4000 rpm (yeah right).

Note: Do not exceed two-thirds of the vehicle's maximum speed in 5th gear.

Do not use full throttle or the kick-down position of the accelerator pedal at all during this period.

Remember that the break-in rules apply to other mechanical assemblies such as the transmission or rear axle, and not just to the engine.

Should any such assembly be replaced at a later stage in the car's life, the break-in procedure must be repeated.

(that bold line was bold in the text)
But everyone knows BMW is a little over-the-top on things like this, so basically don't drive it too harsh for a few weeks and you'll be fine.