When breaking in a rebuilt engine, how many miles should you put on it? I've heard many things, from 1000 to 3000. I think I would go to at least 2000 before really pushing it, but what do you guys think? Also, how does letting the car idle equate to miles? Like x hours of idling=? miles? Also, is letting it idle for long periods better, or actually driving it?

 

I'm at that stage now. If you're re-using bearings, the break-in time will be considerabely less...as low as 500 miles on some engine's. However, if you have new stationary gear/rotor bearings you'll notice that your oil pressurre probably considerably higher than normal. You'll need to actually DRIVE the car(driving will put a load on the engine)in order to breakin the bearings properly. Once your oil pressure drops down to 2.0 kilos(39psi~) the bearings are broken in, change your oil and go!!!

 

yes if the bearings are reused, you can break-in the motor a lot shorter then brand new bearings. according to mazda comp, 100miles is what they recommanded. That is 25@6000 + 25@7000 + 25@8000 and 25@8500 = 100miles.

They also mentioned idleing the car about 30-45 minutes.



I personally think having the first 100miles should be kept under 3000rpm. and after that 500miles under 5000rpm. gradually build boost after 300miles, and change oil after first 500miles. Get all that junk from rebuild out of the engine.