i was reading online on the best ways to break in a new rebuilt engine and i came across two very different method and im wondering which would be the best.

one method states to WOT on the engine and quickly decelerate varying speeds as much as possible for the first 300-500 miles or so to break in the piston rings

another states that light throttle and quick burst of speeds and slowing down quickly.

any ideas?

 

I have heard/read both too...I’m not really sure. Iv always read that when you do valve train you WOT the crap out of the engine to seat everything right. But that could be just hear say. I have also heard the wot on rings too...soo I’m not really all the sure...Iv never personally broke in a engine so I can’t tell you for sure...hopefully someone else will chime in.

 

I'm interested in seeing the ideas some of our members will come up with.
I've had a couple of new engine installs over the years and never did anything but drive them like normal, changed the oil after each 500 miles 2 x's and then it was done...now these engines were 426 Mopars by the way...

 

Well the way ive always heard to do it, is to start the motor and let it warm up completely, then when at operating temperature, start out with
high power loads(wot second gear pulls) for short periods (to avoid excessive heat). The use of low power bursts does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will oxidize this oil film so that it creates glazing of the cylinder walls. When this happens, the ring break-in process stops, and excessive oil consumption can occur. The bad thing is that extensive glazing can only be corrected by removing the cylinders and rehoning the walls. You need to find a happy medium where you are pushing on the ring hard enough to wear it in but not hard enough to generate enough heat to cause glazing..
We have used this form of break in on several rebuilt motors, 5+ and never had one go bad... Except one camshaft, that didnt get broken in properly and got some flattened lobes...