Piston ring break-in

[chaztg]

I've got all the parts to reassemble an L28 motor as part of an old school E88 head / L28 block combo project. I've got .040" bored over pistons on stock L28 rods and the rings my machine shop obtained for me are the chromoly type which I believe are standard for OEM. Does anyone have any suggestions on how to properly break in / or bed-in these kind of rings when the motor is first running? A friend of mine told me that he likes to lug a freshly built motor while driving up an incline or hill a few times to allow the rings to seat. Would this practice be okay for both cast iron and chromoly rings? Any feedback or opinions would be greatly appreciated!

[Diseazd]

Upon initial start-up, keep the rpm's above 2000 for the first 20 minutes. When you take it for it's maiden ride, vary the rpm's and let the engine drag you down in your lower gears a number of times.

Edited December 24, 2011 by Diseazd

[Zealous]

This was recommended to me:

http://datsunzgarage.com/rebuild/index.htm

Scroll down to first time start up

[Zed Head]

The 20 minutes at 2000 RPM seems to be the standard procedure for breaking a in a new cam shaft. As far as breaking in the rest of the engine, I believe that the focus is on getting the rings to set to the cylinder walls properly and that will be more dependent on the type of rings and the cylinder wall finish, which should be specific to the type of ring used.

I would look for the ring manufacturer's recommendations. There are a ton of custom "this is what I do" break-in procedures out there, like your friends lugging procedure. Many of them are based on odd, incomplete ideas about how an engine works, and what happens during break-in.

You might have answered this in a previous post (I can't remember for sure), but why are using the E-88 head on your L28? Did you modify it with the the bigger valves? An N42 or N47 will give you the same CR but with bigger valves, for more power. Just wondering. Good luck.

[chaztg]

Thank you for the replies and for your advice. I looked up the ring mfg website and it had just the info I was looking for. My initial presumptions were somewhat off and I also wanted to clarify that the motor has a .020" or .50mm overbore (Duh!). The cylinder head choice was due mainly to the fact that I have a rebuilt E88 sitting on the shelf, but the suggestion about the similar CR vs an N42 head including the advantage of bigger valves makes more sense I have to agree with. I do also have an extra N42 head I could rob the valves out of, but it's more machine shop cost to do it. However, the 280 head hasn't been rebuilt either, so I'm still weighing the options based on available funds. I've already spent hundreds so far for the junkyard L28 shortblock, the machining cost, new pistons, rings, bearings. It's all fun for me, and the money was spent over time not really on a budget per se. But if I have a ready to use part, like the E88 head for instance, then I should just use it since this won't be a race motor. I learned also that my word "chromoly" may be applicable to BMX bikes from my youth, but there are 3 distinct piston ring types: "chrome" and "moly"(short for molybdenum) are 2 of them and I have CHROME rings, which refers to the top ring only. The breaking in procedure involves setting the base adjustments on the motor, running it up to operating temp, checking oil psi, shutting it off then rechecking the settings (valves, timing, ign, carbs). The next step would be running it for a series of full throttle pulls from 30 to 50 mph. No lugging was expressly stated on the ring mfg guidelines. So I have indeed learned. I appreciate the everyones' help!