How do you properly break in an engine?

 

I don't really know any kind of technique, but it's a 5000 mile process, or something.

 

All I do is fire it up and let it come up to temp, then change the oil. After that I drive it around for a few miles, again letting it come up to temp. This is all time to check for leaks and such, drive at different rpms etc. After that I let it cool down and repeat. The rings will seat after a couple of heat cycles, the bearings as well. Change th eoil and your ready to go. I have never broke an engine in for 5000 miles, that seems just silly to me. Everyone beleives different things when it comes to this subject. I feel the engine is ready to go after a few heat cycles and will be fine IF it was machined and assembled correctly, if it was not, no amount of prolonged break in will help it.

 

With full roller assemblies a full break-in is not as important as it was on the mechanical tappet style engines. I agree with JD, as long as you put it through a few heat cycles it should be fine.

 

They're right about a few heat cycles and you're ready to go, but you won't be seeing all your cars ponies until it's got a few more miles on it. I meant you'd probably be into your prime around 5000 miles.

 

with a sledge hammer

 

As JD mentioned, it is most important that the engine be machined and assembled correctly. On a roller cam engine, go through several heath cycles, change the oil & filter and it should be ready to go. On a flat lifter cam, the usual procedure is to run the engine at around 2000-2500 RPM for 1/2 an hour to get the lifters and the cam lobes mated. Then do the same as for the roller lifter engine. It is a good practice not to run the engine at a constant speed for the first 500 or so miles in order to better lubricate the rings till they are seated. Allowing the engine to coast down from a higher speed creates high vacuum which draws a little extra oil through the valve guides and helps to lubricates the top of the cylinders.