Engine break-in after initial run Options

[Cevan]

I've searched here and at other sites for engine break-in procedures. I've done the cam break-in and the motor is now in the car with fresh 20-50 Brad Penn and a new oil filter. Valves have been checked. Fingers crossed.

From what I've gathered, most recommend warming up the engine and then doing a series of fairly hard accelerations under load followed by de-accelerations to help seat the rings, and in between, no sustained rpm driving. Some go as far as recommending you drive it like you stole it and others (Aircooled.net) say drive it easy for the first 100 miles.

I also tried to determine when best to change the oil. Do I need to change it at 100 miles and then again at 500 miles (and then every 3000 miles thereafter)?

[PRS914-6]

Lets go over a few things......

The cam manufacturers want you to keep a nice steady medium RPM load to break in the cam and lifters, the worst scenario for the rings (but they only care about their cam). Slow rotation has a tendency to "gall" new cam components.

New engines built these days are built to much tighter tolerance than the old days. You notice that they run 5-30w oil and still have good oil pressure.

You can't use your owners manual as a reference to break in for a "rebuilt" engine. You don't have the machinery that the factory did to machine, assemble or break in the engine. Your case is not as straight, the holes not as round, the crank not as straight etc etc....

Now for the important (in my opinion).....Rings. Get it wrong and have a smoker or lower compression.

Rings seal not by the pressure of the spring action of the rings but gas pressure BEHIND the ring. When the engine fires, gas pressure pushes downward on the ring, works behind the ring and the pressure forces the ring outwards to seal against the cylinder. Ever notice the wear on the top of the cylinder is always worse than the bottom? That's because the top has the most gas pressure behind the ring.

When an engine is new and the cylinders freshly honed with new rings there is only a short period of time to "seat" the rings. The cylinders quickly "glaze" in a very short time making ring seating difficult. The key is to wear the high spots off and make a good seal to the cylinder wall as quickly as possible. I have torn down many a race motor and I can assure you the cylinders glaze faster than you can imagine.

For the rings to seat they need gas pressure and that means stepping on the throttle. That action generates localized heat though. The key is load and then unload to cool.....repeat, repeat, repeat. Let it cool down and start over. The worst thing you can do is to putz around town with tender loving care never stepping down on the throttle and never exerting pressure on the rings. Yeah everything will break in real nice except the rings!

Sitting in your garage running for an hour is the WORST thing for a new engine. Get it going, get it on the road and get on and off the throttle avoiding high RPMs. Accelerate hard then get off the gas for a bit....It won't hurt that cam you are so worried about.

Please see my comments in This Thread

I hope this long-winded response will help those understand what's going on when their engine is new