Engine break-in, any suggestions?

[Pir0San]

So I'm going to rebuild my L24, the guy who gave me the block said the car smoked due to valve guides, but it turns out it smokes because two of the six oil control rings are not doing their job, and the car is burning oil. I've been reading around, doing price lists, and so far I've determined that with AE Clevite Chrome Rings, AE Clevite Main and Rod bearings, Felpro gaskets all the way around, I'm looking at approximately $245.42 w/tax, as well as $80 in shop fees (cylinder honing, hot tanking, crank micropolish). Does this sound reasonable to anyone? How often is it that a motor needs to be bored out? The last time I saw inside of the cylinders (500 miles ago), I didn't notice any ridge or anything serious, so honing should be the solution for ring break-in, right?

So, my original question: How do you break-in an engine properly? I know I can't just go out after rebuilding my engine and beat the hell out of it, but I've read so many things that I'm confused as to what the honest truth is. I've read this article : Mototune break-in, as well as this thread Break-in, and they slightly contradict each other. The mototune article says that in order to break an engine in properly, the car needs to be warmed up and driven under load. The article doesn't say to go out and red line the engine, but it does say the engine needs to be put through it's paces. The thread on this site says that the RPM's need to be kept under 4000 RPM's in order to break-in, but which one is right? From what I understand, you must not keep the engine at a steady RPM while break-in is occuring, due to the fact of the cylinders only expanding and seating at a certain RPM. I even took a look at the book "How to rebuild your Nissan and Datsun OHC Engine", and the author says to keep the engine under light load. I don't know what to believe, and I'm sure engine builders will give me varying answers.

So, what's the right answer? I just want to do it right, have an engine that doesn't burn oil, as well as an engine that puts the power down that it has potential to make.

Also, are Sealed Power rod bearings any better than the AE Clevite bearings? From what I understand, Sealed Power and Federal Mogul used to be the same company, and Nissan used Federal Mogul parts when assembling the L-series engines.

[240ZX]

Well, I'm certainly no authority on the subject but, can offer up this bit of info.....One thing you should pay close attention to is, if you are planning on installing chrome rings, I believe they require a specific cross hatching (and specific stone grit) of the cylinder bores in order for the chrome rings to seat properly. If done incorrectly, they maynot ever seat properly. On the other hand, cast iron rings will seat rather quickly in a cylinder with just mild honing. Also, as far as the rpm during break in goes, keeping it under 4K sounds correct but, many an engine builder has recommended short periods of run time, under a mild load, at various rpm below the 4K rpm. It always best to contact the ring manufacture for their recommendations.

[Pir0San]

from what I've read and been told, chrome top ring sets are great for longevity, but as you said, do need to have the correct honing procedure done to them. Does anyone know the lifespan of a cast iron ring as opposed to a chrome ring, and which one is better to go with? I don't mind spending a few extra dollars for chrome top rings, which is why I selected them.

[SteveK]

Consider using gapless rings (topseal) etc, I have been using them for the past year with excellent results.

[kenz240z]

I had my engine rebuilt (L24) last Spring. The rebuilder suggested keeping it under 3500-3700 rpm for the first 500-750 miles. Change the oil after 750 miles. Don't cruise at the same speed/rpm. Varying load, but don't overdo it.

I've followed these instructions, and now have about 850 miles on it. Runs like a top!

[Pir0San]

It seems to me that the general consensus is to give the motor 3/4 throttle and only go to 3/4 of the redline rpm, so therefore you would go through all gears, rev to 4500-5000, shift, and do it all over again, without lugging the motor, and downshifting and letting the engine do most of the braking instead of using the brakes totally. I just want to get the full performance and reliability out of my Z!