Break-in procedure tips?

[efhughes3]

I've been studying various write-ups on this topic. Wayne's book suggest 20 minutes at 2000 rpms to break-in the cams and then changing the oil before going on a first drive. But, I think that some would argue that this doesn't help seat the rings. The need there is accel/decel to prssurize both sides of the ring to seat them.

Should I maybe start it up, run it in the driveway for a few minutes checking for leaks, etc, and then take her for the first 20 minute drive to get the rings seated?

Let's start some dialog on this...

[cgarr]

Run it hard, not red line but 5ish, don't baby it for Gods sake. dialog started:

[304065]

Ed,

As far as "breaking in the cams" goes, the amount of valve spring pressure is pretty much a constant so you can get the same effect, starting the process of wearing the cam lobes and rocker faces against one another, whether the engine is at idle or at redline. (Obviously if you are floating the valves you're outside the envelope of break-in operation) So I wouldn't run the engine at idle for any length of time to facilitate that.

I would warm the engine up by gently driving to a country road without much traffic. Then drive it like an NYC cab driver: full throttle in 2nd or 3rd gear to 5K, lift for a second, stand on brakes. Full throttle, stand on brakes. You want to achieve high cylinder pressures and plenty of vacuum on the overrun. Obviously personal safety and regard for Law and Order take precedence over the ideal break-in but you get my drift.

[efhughes3]

I think we're on the same page on the drive portion, I guess you're confirming that maybe the 20 minute "high idle" isn't needed. I'm not leaning to a short run in the driveway on the first start to check that all is well and to yell yeeha and grin from a job well done. Then, it's off for a drive.

One note though, shouldn't one allow the engine to do the braking to get the full effect of the vacuum?

[304065]

Ed, engine braking would be better, I was thinking more along the lines that with stock 915 III-NT-23/29 and IV-QQ-26/26, a 7:31 and 24.2" tire, you'd be doing a cool 64 and 81 mph at 5,000 rpm. Then again you DO live in Texas, it's not like it's FDR drive or something.

[cnavarro]

http://www.mototuneusa.com/break_in_secrets.htm
http://www.aircooled.net/gnrlsite/resource/articles/engnbrkn.htm

[gigem75]

"Drive Friendly, the Texas Way" Dolph Briscoe, former governor of Texas and on all the signs welcoming you to Texas.

I've got the perfect rd for you, FM 782 from Henderson going north through a lignite mine. Great road, long curves, and you can see ahead for miles!

[dtw]

I've been wondering about this too. I'm doing a 2.7 rebuild right now, but the cams and rockers looked fine, so I'm reinstalling them as-is. Rockers were bagged according to position, so I will have all the rockers back in the pre-rebuild positions. No break-in required - so I've been thinking I'll just skip the 20-minute deal and hit the road. Thoughts?

[efhughes3]

Charles, thanks for the links.

I'm still kind of confused, however, as there is a lot of conflcting info out there. In fact those two links are about 180 degrees apart.

I've got new cams, rockers and rings. If you do the 20 minute high idle for the cams and rockers, that seems to be not as good for the rings, as there is no load on the engine.

If I start it, check for leaks, and drive it with the accel/decel mode under 5K for 20 miles or so to get the rings seated quickly, do I do disservice to the cams/rockers?

[gigem75]

I wonder if anyone has ever torn down their freshly rebuild engine and documented the condition, rebuilt it, started it, driven it a different way, torn it down again, documented it, etc etc. point being, start it, let it warm up, check for leaks, listen to it, then drive it at different speeds, break it in at different speeds, then take a trip. IMHO

[jpnovak]

Ed,

Great job on the rebuild. Hope to see you at the track in the Spring.

I agree with the drive it hard group. I think I would use the "high-idle" method only to look for leaks and verify timing. This is not really needed with a Motronic car. So, as long as you have no leaks, take it for an easy drive until it warms up and then build as much cylinder pressure as you can. Foot to the floor to an rpm point above your peak torque value (around 5K for a 3.2) and then snap closed throttle. Rinse and repeat for as long as the road allows.

Closed throttle decel down a hill is supposed to work really well.

[Jeff Alton]

The decel is very important and should not be overlooked. High vacuum creates pressure on the other side of the rings and sucks oil up into the cylinders. All I have been doing for 400 miles is this type of driving.

On my motor we ran it at a high idle while we screwed around with the computer setting base timing and injector pulse. Then on the dyno it went for 3 sessions of accel and loaded decel.

I changed the oil/filter after about 20 mins of total run time, again at about 125 miles, again at 300 miles and am doing it right now before it heads back to the dyno for the full power tuning.

You should feel the motor get stronger (sepecailly the engine braking while deccelerating) as you put the miles on during the first drive.

Keep an eye on temp as well. Don't take it much above 3k until you have some oil temp and do not let it get too hot. Also, do not lug the motor (not that you should with a broken in motor anyways) but DO NOT lug one with new cams/rockers.

Cheers

[efhughes3]

Thanks gents. I think I'll start it for the leak check and then drive it to round out the first 20 minutes, then back home to change the oil.

I started to put the engine back in today (I'd dropped it without the trans) and cannot find enough front-back room to get it back in. To clear the spindle with the TO bearing and the mount studs requires the engine to be too far back into the rear body sheetmetal.

I'm thinking about taking the fan pulley off to buy that small bit of room, but I should probably just cut my losses and drop the transaxle, and mate it outside the car, and put it back in as normal. I thought having the car on the lift would make this all feasible, but the clearance is a big snag.

[gigem75]

grab some c/v joint gaskets if you do drop the t/a

[88911coupe]

If I did not replace the cams or rockers does that mean I don't need to bother with the 20 minutes of idle time? Mine all were in perfect condition and everything measured in spec. Am I to understand the 20 minute idle is specifically for the cam/rocker arm interface to set up? I put everything back exactly where it came from so that should not be an issue in my case. Am I missing anything?

[911 tweaks]

better safe than sorry... I feel that any and all engines that have invasive procedures, should be re-broken in to some degree... again, better safe than sorry...
just my 2 cents worth not asked for
Good Luck and report back how it all works out!
Bob

[tctnd]

The "high idle" is SOP for break-ins on any 4-stroke, not just Porsches. The intention is to insure that plenty of oil is splashing around to lube the came lobes and lifters as they wear into a mated state. In the "old days" people would often start a new engine, set the idle, and let it run for an hour to gently break it in. That was fine for everything but the cams which were lubed mostly by splash and could suffer during this critical period if not well oiled.
regards,
Phil

[Wayne 962]

The 20 minutes also helps to make sure the engine is up to operating speed. I'm about to startup a new 996 engine tomorrow. I will let it run for less time because this is a water-cooled engine, and will warm up to operating temp a lot quicker. I would keep with the 20 minute or so warm-up / wear-in period...

-Wayne

[cnavarro]

Here are some good tips on break in:

http://www.mototuneusa.com/break_in_secrets.htm
http://www.aircooled.net/gnrlsite/resource/articles/engnbrkn.htm

We successfully broke in the new 2.9 engine for my wife's Boxster using Brad Penn 30wt break-in with no issues. I'd have to say on this fresh engine, the first drain was the cleanest oil I've ever seen out of a fresh engine.

[88911coupe]

I was leaning towards doing the 20 minute in the garage anyway since it would allow me to keep an eye out for fuel or oil leaks or any other issues that might crop up. I'm running out of excuses to put it back in and fire it up...I'm just going to have to bite the bullet and go for it. There's no way in hell I'd have even considered doing this without Wayne's book.