Break-in: Why 2k for 20min and no redline?

YTNUKLR · YTNUKLR's Garage

I am by no means challenging what Wayne says in his book, but I was just curious as to why one would run it at a constant 2k for a whole 20min, the very first time it's ever started. Also, if running it thru the rev range a lot is good, to get the rings seated at a variety of rpm's, why not take it to redline? I think it said don't run it above 5k? Why? Thanks

Wayne 962 · Wayne 962's Garage

a) run it at 2000 rpm to get full oil circulation and intro wear on some of the parts. There is much debate about this subject, but most people seem to recommend this method

b) redline is very stressful, and your engine is not fully worn in until about 1000 miles or so. Running at high wear in the early stages can accelerate wear patterns that will shorten the life of your engine. This is one of the reasons why race motors have engine lives that are measured in hours, not miles...

-Wayne

jluetjen · jluetjen's Garage

Or option two if you can't wait 1000 miles, take it to the track for a session after you've run it in a little at 2000 RPM as Wayne suggests. You'll see your temperatures go up as the engine beds in (from the extra friction of the new rings) and then settle down again. Once the temperature has settled back to normal the engine is broken in.

MT912RS · 03-17-2004, 07:24 AM

This is an interesting take on the whoe thing. Makes sense. Seems like there are a lot of theories but not much data to support it this guy uses some logical reasoning. http://www.mototuneusa.com/break_in_secrets.htm

Ho Hum 74 · Ho Hum 74's Garage

That's interesting. I have heard that Wayne's method is more appropriate when you've had a top end rebuild to allow the valve-train hardware to settle and bed in. When you've just done a lower end rebuild I've heard the best thing to do is get out there and drive it hard like this article says.

cstreit · cstreit's Garage

The 20min/2000k method is recommended frequently when new cams are added into the system. This allows them to get plenty of oil as they are initially seating with the rockers.

This is usually documented any time you buy new cams.

MT912RS · 03-17-2004, 09:56 AM

I have read that the elevated RPM for cam break in is so that the inertial forces of the valve train parts help to counter some of the high spring pressure on the rocker/cam interface and allow the cam and rockers to burnish a hard surface with lower pressure, preventing galling. As the cam pushes the valve assy open the weight of the associated parts wants to continue opening the valve as the cam clears its highest lift point effectively relieving some pressure on those surfaces.

Wayne 962 · Wayne 962's Garage

I recommend driving the car hard, but not to the point where you're going to start to wear things prematurely...

The link from the Mototune guy is good - it's basically what I recommend doing in the Engine Rebuild Book. The initial 20 minutes are important because you need to get oil pressure built up and you also need to completely warm up the engine (as he has stated many times in his site).

-Wayne

aigel · aigel's Garage

"Breaking in the cam" is done at a higher rpm (vs. idle) because the forces on the cam / rocker surfaces are actually lower at higher rpm. On a side note, on the pushrod V8s it is done the same also because the oiling is much better and people believe that it gets some splashing oil from the crank too.

On the 911, of course there are oil sprayers in the cam housings, I'd assume that they spray a lot nicer at elevated rpm also, helping to break things in carefully.

For piston ring seating, dyno stand break in or driving it is recommended. Of course only an air head would come up with the idea to just drive the sucker. A water cooled setup, most people want to see it up at temp at least the first 20 minutes of cam break in, to make sure there is no bad surprises. (leaks!)

George

Steve@Rennsport · 03-17-2004, 11:01 PM

George is right on the money,...

Its all about getting LOTS of lubrication and cooling on these highly stressed parts while they become "happy" with each other.

Seating rings really requires either an engine dyno or some specific procedures to burnish the ring's surfaces to achieve maximum cylinder pressures and low oil consumption.

YTNUKLR · YTNUKLR's Garage

The elevated idle now makes perfect sense. But, to be sure, on the max-rpm limit, 5k is tops? Due to premature engine wear? What is the "ideal" way to breakin a motor? Thanks!

snowman · 03-19-2004, 10:52 PM

The Ideal way to break in a motor is to:

1. Run the motor at 2000 to 2500 RPM for 20 minutes. Breaking in the cam.

2. Making several FULL throttle accelerations/decellerations to seat the rings.

3. runing the engine easy until the temp stabilizes, ie no longer rises abnormally. and oil consumption stabilizes. May take up to 12,000 miles worst case.

Alternative breakin of rings- use flex hones, rings will be broken in withing the same 20 min the cams seat.

Ho Hum 74 · Ho Hum 74's Garage

Guys,

I'm planning to go to the track fairly (read a few days) shortly after my rebuild. Should I not be taking her up to 6,300?

T

Steve@Rennsport · 03-20-2004, 12:37 PM

Ho Hum:

If it were my engine, I would get at least several hundred miles on it and follow Jack's procedures to break in the motor before you track it.

You must NOT get it hot, no matter what. Keep those oil temps at or below 210 deg F, regardless if you want it to live a long time.

jluetjen · jluetjen's Garage

So Steve, if you recommend putting several hundred miles on it BEFORE you track it, how would you break in a track motor? "Several hundred miles" would be a couple of weekends of track mileage.

Steve@Rennsport · 03-20-2004, 04:11 PM

Hi John:

LOL,...Each and every race motor we build is broken in on our engine dyno and they are designed to be raced after the rings have seated. All of these get 2 full days on the dyno for break-in and power runs.

As you might guess, racing engines do not require-expect 100K mile lifespans and that's why I made my original statements above.

Depending on each individual engines' configuration, these get opened up and inspected every 60-120 hours.

snowman · 08:57 PM

My comments on breakin are for a street engine. What can be done differen't, as in a race engine, so you can go for it just after rebuilding?

I don't know all the answers to this one, but a VERY big one is the final honing fo the cylinders. Use of flex hones, grape hones, plateau honing, whatever you want to call it is key. What these hones do is the same thing rings do, but they do it before you assemble the engine, not after, and much quicker. They knock off the peaks of the metal and make a level sealing surface. Modern, good rings are honed, that is run in during manufacture. So mated with a properly honed cylinder, they are READY TO GO within minutes of operation.

Modern rings is a very important subject here. From what I have heard several ring manufacurers may be using 100 year old technology for their rings. If you use one of these rings you may be in for a long, drawn out breakin period. I do not know for sure which ones these are. But I can say which one isn't, ie Mahle. Mahle rings are state of the art, the others I can't say.

Older Porsches use cam followers, much superior to flat tappet cams. but still a step below roller rockers. Roller rockers do not require a break in period. I am not up to what a modern Porsche uses, but no one (for the most part) races one anyway, except the factory and professionals. I would say that the 20 minute period is plenty for cam followers to break in.

A couple of full throttle accellerations/deacellerations is still required, no matter what you do. But this is just a couple of laps, max.

Everything else, in the engine, should be ready to go at this point. What else is there??

The oil temp is key, IT CANNOT BE ALLOWED TO RISE above 210 degrees F. If it does you have an engine that is not broken in or is under cooled for the intended use.

Which leads to what oil do I use in break in?