Rebuilt Engine Breakin Process

[Dan Owens]

Okay guys,

I just got my rebuilt 3.2 engine back today and I'm putting it in the car starting tonight or tomorrow. I need to know what the proper breakin procedure is for an engine that's been completely rebuilt. Everythings "stock" as I didn't improve or modify anything just back to specs.

Dan

[GIBSON]

Dan, check the search feature for previous threads on this topic, quite a bit has been said. Here's what I just did, others may have variations of this procedure but probably fairly similar.

First engine fill, 30 weight non-synthetic oil. Keep the engine rpm
below 4500. Verify oil pressure and double check oil level when warm and at idle.
At 250miles, change oil, continue using the 30weight. Increase rpm limit to 5000 max, vary the engine speed to help seat the rings (i.e. no long cruises at a single rpm).
At 500 miles drain oil and adjust valves, retorque cylinder heads and exhaust nuts, check for leaks, refill with multi-viscosity oil and increase rpm limit to 5500-6K
At 1000 miles, drain oil, adjust valves if you like and increse
rpm limit to rev-limit. If you are going to switch to synthetic oil you might do it now but some have been waiting till 2K to 3K miles for the switch, others do it sooner.
That's my experience, see what others say.

[Superman]

I was worried that my rings would not seat properly and the engine would smoke. I was afraid of this because I re-used the old cylinders. After checking, it seems that aircraft engine builders routinely use non-detergent oil for the first 50-100 hours, for the purpose of ensuring the new rings seat properly. So, I did this. The engine NEVER smoked. It might not be as important to you if you have new pistons and cylinders.

Bruce Anderson was also worried that the rings might not seat, and his advice was to drive it. Don't let it idle. So I did. I believe the usual breakin procedure involves a high idle for 20 minutes or so before any driving.