Engine Break-In

old_skul · 03-17-2003, 11:56 AM

My buddy got his engine back from the mechanic after a rebuild. The engine break-in done by the mechanic was a lot different than most I've heard about.

For instance, on startup, I thought you were supposed to run the engine at 2200 RPM for 20 minutes, shut down, change the oil, and then restart and keep it between 2000 and 4500 RPM until 1000 miles. Other rituals I've heard involve 2000 RPM for 20 minutes, and then 3000 RPM for 10 minutes, along with a few other levels of revs for periods of time....it's all confusing.

What have you heard is the proper procedure?

(Disclaimer: the mechanic in question is a Porsche industry veteran and worked decades in a Porsche dealership and is a certified Porsche master mechanic. I don't doubt his wisdom.)

esther · 03-17-2003, 12:02 PM

how did your buddy's porsche mechanic break in the engine?
we did the 2000 rpm for 20 minutes and then change oil ...

Wayne 962 · Wayne 962's Garage

Excerpts from Chapter Six of the new book:

As soon as the engine is started, then make sure that you immediately raise the idle to about 1800-2000 RPM. Use an RPM meter hooked up to your spark plug wires if you think that your tachometer may not give you accurate readings. It is important that the engine not be at idle speed for any length of time. On the CIS cars, you can simply adjust the large spring-loaded screw on the side of the throttle body. For carbureted and MFI engines, turn the two idle adjustment screws on the ends of the throttle bodies. If your car is equipped with a hand throttle, simply pull it up until the idle reaches the desired level. For the Motronic engines, your best bet is to just sit in the car with your foot on the gas pedal, keeping the car within the proper RPM range.

Make sure that you take a stopwatch with you. This isn’t an option, but a requirement. The reason is that after about 5-10 minutes, you’ll turn the engine off and swear it was 20 minutes. The 20 minutes will feel like forever, because the engine will be very loud, and you’ll think that this treatment can’t be good for a new engine. Never fear – it is. Running the engine in at this RPM raises oil pressure and oil flow volume so that all your new meshing parts in the engine are sure to get plenty of lubrication. The higher RPMs are best for forming the initial wear patterns between the rocker arms and the camshafts. At this RPM range, the engine is turning over just fast enough that the rockers begin to be thoroughly lubricated as they follow the camshaft lobes. The rockers begin to ride on a thin layer of oil which separates them from direct contact with the cam lobe. At lower RPMs, the valve clearance gap comes into play as the rockers have a tendency to hammer the camshaft. You can hear this as you raise the RPM – the click-clack of the valves will subside somewhat.

When the engine has run for 20 minutes, turn it off, and immediately empty the oil. If you don’t believe that an oil change is warranted after only 20 minutes, then simply look at the oil as it empties out of the engine. You will see millions of tiny metallic flakes in the oil. This is the evidence of all your new parts breaking in and beginning to mesh with one another. Empty the oil out of the engine and the oil tank and replace the filter. Refill the engine with about eight or nine quarts of oil.

If your car is equipped with a front-mounted oil cooler, you should check to see if the thermostat has opened up the flow of oil to the cooler. Feel the oil cooler lines to see if they are warm. If the thermostat hasn’t opened then you’ll have to add about 3 quarts of oil after it opens up on your initial drives.

Now, restart the engine. Adjust the idle down to proper levels (800-900 RPM for most engines). Check the oil level in the tank with the engine at idle (it still should be warm at this point). Add a quart or two if the oil level appears low. Using your timing light, set the timing according to Project 23 in “101 Projects for Your Porsche 911.”

You’re now ready for that all-important first drive. Check the brakes and the clutch before you let the car out of your driveway. Take the car to a location where there isn’t much traffic. You’re going to be quite distracted listening to your engine, and breaking it in – you don’t want too many other cars around. Drive the car varying the load, and the RPM range. Shift gears often and do not let the car stay in any one RPM range for very long. Don’t let the RPMs go above 5000 for this initial drive.

You want to vary the engine speeds because you want all the parts to wear and mesh at all RPMs. Running the engine at a constant 4000 RPM or so will cause the rings to seat fine at that RPM, but not at other ranges. You want to wear the engine evenly and consistently, particularly on this first drive.

On your first drive, take it out for about a 3-5 mile drive. Stay close to your ‘home base.’ You want to be able to return quickly to your garage and tools if you encounter a problem. After the first drive, return back to your garage and check the oil lines, carburetors, oil temperature, etc. Make sure that nothing is amiss. Check the oil level – if your thermostat has opened up, you will find that your oil level is now probably about 3 quarts low. Check the oil using the dipstick, not the gauge, and only check it when the car is warm and running at idle.

Etc. Etc. Etc...

-Wayne

Wayne 962 · Wayne 962's Garage

There is no one correct way - many methods will work. The one detailed in my new book appears to be what most people do, and also is proven to work well all of the time...

-Wayne

old_skul · 03-17-2003, 01:39 PM

Wayne, it was actually some of the sample pages from the book that inspired the post. Yesterday's first start was nothing like this. There was a lot of engine revving and the recommendation was for an oil change after 200 miles, along with a valve adjustment.

After the initial startup and perhaps 5-10 minutes of engine revving and mixture adjustment, the car was shut down. We then went for a 1 hour drive on back roads with many RPM range changes (as you recommend). There was also no recommendation of top limit - he said to take to to redline occasionally. Shrug; I guess it's whatever pleases the rebuilder

RickM · RickM's Garage

I'm curious about the use of Synthetic oil during the break-in process. It seems the factory does this now. Or is the 20 minute break-in period different from the break-in an owner does after delivery of a car.

Doug Zielke · 03-17-2003, 06:08 PM

The rings will never seat to their optimum performance level, if you "baby" a new motor.

Once you have determined the oiling system is delivering full pressure, drive the motor "briskly", with lots of acceleration *and* deceleration.

Varying the rpm and load is the key to a successful break-in.

cstreit · cstreit's Garage

I've also been told that you must allow for engine decelleration as well as acceleration in order to put reverse gas pressure on the rings...

Key point is that gas pressure on the rings, NOT spring tension breaks them in. Rings only put 5-10 lbs of spring pressure on the cylinder walls... It's the combustion gasses that really press them to seal.

Don't baby it. Progressive throttle pressure, don't lug it...

kstylianos · 03-17-2003, 06:47 PM

Chris,

You are correct. I was talking to Steve Weiner this afternoon regarding breaking in new rings in Nikasil cylinders. If you can't get the cylinders honed (with a diamond cutting tool) then the following process usually is successful for breaking in new rings in old Nikasil cylinders.

Clean the cylinder walls and get them as shiny as possibly. Full throttle from 2k to 5k in 3rd or 4th gear, then decelerate back down to speed. This should be done at least once every 10 miles. Also varying RPM's as much as possible is also recommended. The pressures of WOT at low RPM will force the rings against the walls at the highest pressure possible, giving them the best chance to set. He recommended doing this process each time driven about 2K miles....yikes. Sure beats new Mahle's though.