breaking in rebuilt engine

whats a good way to break in rebuilt engine cat 3066 excavator.

This is something we used to use on off-highway truck engines, so you'll have to adapt it somewhat to an excavator because it's designed to use torque converter stall. It will also depend to some extent on the ambient temperature.
Minimum of 10 mins @ low idle - minimum load. Coolant temperature must be in normal range before proceding.
15 mins @ approx 900 RPM - 25-30% load
15 mins @ approx 1200 RPM - 50-60% load
15 mins @ full RPM - full load.
If the coolant temperature rises too high at any point in the procedure, remove the load and run the engine at somewhere just off idle until the temperature returns to normal. Then resume the procedure.

thank you ill print it off and keep it in the cab.

drive like borrowed, it will run or fail in very few hours. most of time will fail in about a day or it will run long time.my two cents.

dozr, Is there a difference between borrowed and stolen?

The problem I've had with excavator engines was getting enough load on the engine for a long enough time to get the rings to seat well. On a couple I've paid to have them run in on a dyno. On the Komatsu line that I am familiar with I just turn up the output on the pump to pull the engine down a couple of hundred RPM and then work the implements all at once all the time for about an hour. Reset the load screws back to factory and put the machine to work. What ever you do, don't let the engine idle for long in the first 100 or so hours.

Thanks for the advice

Good advice from John.
I should've pointed out that the info I posted above was for an engine that had not been started after being rebuilt, and that was being started for the first time while installed in the machine.

By far the best options is to do the break-in procedure on a dyno, although for the length of time it involves you may well end up paying for additional dyno time over and above a normal engine load test. The equivalent dyno procedure would be as follows, takes about 75 minutes, and would be carried out before the formal dyno test of the engine: -

5 mins @ Low Idle
10 mins @ 50% Max rated engine speed & 20% rated load.
10 mins @ 75% Max rated engine speed & 30% rated load.
10 mins @ High Idle & 50% rated load.
10 mins @ High Idle & 75% rated load.
10 mins @ High Idle & 90% rated load.
10 mins @ Max rated speed & 100% rated load (full power RPM in other words, not High Idle)
5 mins @ peak torque RPM & @ peak torque load on dyno.
2 mins @ High Idle with minimum load.
2 mins @ Low Idle with minimum load.

As nobody mentioned yet, I was always told to use conventional oil not synthetic for the break in. Supposedly synthetic is too slippery to allow the rings to seat.

Might be a load of rubbish but that is what I’ve done along with a plan as listed above and never had a problem.

I use conventional oil in all my equipment as it is older equipment i change oil frequent.I dont have access to a dyno anywhere close to me so will turn the pump up as John mentioned.

Ct Farmer said:

As nobody mentioned yet, I was always told to use conventional oil not synthetic for the break in. Supposedly synthetic is too slippery to allow the rings to seat.

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As a kid I vaguely remember my older family and friends talking about breaking in engines with pure mineral oil. It stemmed from my grandfather being a B-25 mechanic and this was their procedure for breaking in new radial engines. That logic trickled into breaking in rebuilt 2-stroke motorcycles, 1960's V-8 muscle motors, etc. The logic was the mineral oil was just enough lube to keep the journals in good shape while allowing the rings and rod guides to seat from the lack of wear additives. I also remember the 'drive it like it's stolen' with attention to constantly varying the rpm.

I never broke in a new engine (other than buying a new vehicle) so can't attest or recommend using mineral oil. Point is if you're going to use conventional oil, consider that the wear additives may be working against you if you use premium oil. You'll probably change the oil soon after break so maybe a not-so-premium oil is something to consider. One thing I didn't see so far is when you should to change the oil after the above procedures.