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Can anyone tell me what the break in period is on a rebuilt motor. I have heard 500, 1000, and 1500 miles. Which one is it. Also I have heard that you should stay around 45 mph, I have also heard that you should take it all the way up to 65-75 and bring it back down. What is the safest way of doing the initial break in?
 

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Break-in period

According to most auto manufacturers, you should stay under 55MPH (reduced RPMs) for the first 1,000miles.

This allows components like the new rings to wear into the cylinder walls to create a good seal. Also should change oil at 1,000 miles to remove metal shavings from the engine. Synthetic oil would be the best way to start a new engine on the right wheel... :wink:
 

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The instructions I get from the machine shop where I've had my engines rebuilt go like this: straight SAE 30 weight oil for the first 500 miles followed by a 10W30 for the next 2500. Switch to synthetic after 3000 miles. Also, if the cams have been polished or ground, its important to run the engine rpm up to between 2000-2500 and run for 10-15 minutes straight as soon as possible to break in the cams. Vary the speed while driving that first 500 miles - i.e. no long road trip right away. Good luck.

Phil D.
 

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the way I break my engines in is that I drive them 250 miles under 55mph and/or under 2.5K rpms then I do an oil change. Then the same at 500 miles, and another oil change. Then another oil change at 1000 miles.
 

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I always do the very first oil change on any new engine at 500 miles, followed by a second oil change at 1500 miles. The larger break-in particles that occur during the first 500 miles can sink to the bottom of the oil pan sump and not get filtered out by the oil filter. This is where a drain plug that has a magnet really comes in handy. :) A new engine that has all new parts (including cams) can actually take quite awhile to fully break-in. I usually wait about 8,000 miles minimum before switching over to synthetic oil to give things plenty of time to fully seat and wear-in properly. The cam lobes and rocker/lifter surfaces especially need ample time to fully lap-in and become mated surfaces.
 
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