Engine break in opinions

[TwoJ's]

Here's a quick back story: My good friend has an '88 m3. he was getting loud "death rattle" (timing chain slap) from the s14. Finally one day the car just shut down while shifting from first to second, and then the motor simply wouldn't turn over.

I wanted to drop the pan and see what was up, and possibly pull the motor and do a rebuild with him, but he is a wealthy bastard and he just had it towed to a shop. Long story short, the timing chain guide plastic thing failed the forebode the motor from turning over. The shop dropped the pan and the #2 main bearing was toast. He gave them the go ahead and they ordered the TMS 2.5 kit and rebuilt it.

So we went to pick it up a couple weeks ago and the shop owner told him to keep it under 5000 rpm for 500 miles. Now, this is contrary to what I've heard about breaking in an engine. From what I've read, it's common practice to bring an engine to a relatively high rpm and then let it decel while still in gear. This supposedly helps seat the rings to the cylinder wall.

So I did some reading and it seems there are many varying opinions. So what have you guys done? Take it easy to break it in, or run it hard? I've never built a motor, so I have no experience with this.

Oh, and even just up to 6000 RPM, the 2.5 feels MUCH better than the old, tired 2.3.

[James Crivellone]

New Motor

First 300 miles on regular organic oil, vary RPM and Load.

After 300 miles, change to synthetic, and beat the shit out of it.

[BenM]

Also, find a hill, gather some speed, then downshift and let the engine decline in revs. Either that or use a dyno. I've heard it helps on boosted engines, maybe NA motors too.

[BenM]

vary RPM and Load

Wait, nevermind. I'm a dumbass

[TwoJ's]

Thanks guys. It's got roughly 300 miles since the rebuild and he's been getting on it, but not bringing it over 6k or so. I think it's time for an oil change and a run down Canyon Road to Yakima. It's just starting to get nice here too.

Too bad he's got the snows on it still though...

[PiercedE30]

Do this 20 times: First gear, throttle on the floor up to about 1000 under rev limit, and let it deccel down to nearly die-ing. Change the oil and be done.

[mrsleeve]

Drive it like you stole in the 1st 20 miles, if not you will have a dog. And might not get the rings too seat well.

[blunttech]

Drive it like you stole in the 1st 20 miles, if not you will have a dog. And might not get the rings too seat well.

agreed, drive it from day one like you plan to drive it. i always run a motor a few hours and dump the oil after a rebuild but i beat the shit out of it right away.

[TwoJ's]

So aside from breaking it in with the right foot and an oil change, should a valve adjustment be done some time soon after it's been "broken in"? When I rebuilt my head on my m20 I did a valve adjustment before running it, and had to do it once more about 2000 miles later. It's been good for the 10k since, so I'm not sure if I just didn't do it right the first time, or if it's something that should be done.

I know I'm talking apples and oranges with the s14 vs. m20 and valve adjustments, but I just don't know. And as always, I'm just curious.

[DCColegrove]

New Motor

First 300 miles on regular organic oil, vary RPM and Load.

After 300 miles, change to synthetic, and beat the shit out of it.

The correct answer.

[WillisE30]

So aside from breaking it in with the right foot and an oil change, should a valve adjustment be done some time soon after it's been "broken in"? When I rebuilt my head on my m20 I did a valve adjustment before running it, and had to do it once more about 2000 miles later. It's been good for the 10k since, so I'm not sure if I just didn't do it right the first time, or if it's something that should be done.

I know I'm talking apples and oranges with the s14 vs. m20 and valve adjustments, but I just don't know. And as always, I'm just curious.

You shouldn't need to adjust the valves after a rebuild. The clearances aren't going to change significantly during break in. The break in period is mainly for seating rings. Honestly for a street motor, taking it a little easy in the first few hundred miles isn't a bad idea. Stories of rings not seating correctly and glazing seem to be more myth than reality based on what I've seen.
Now with a billy bad ass race motor the hard pulls and decel method you mentioned is definitely the way to go.

[mrsleeve]

street or race, brake it in with the right foot firmly planted to the floor often. Or you will end up with a dog, or poorly seated rings. Oh yeah plus 1 on the dino for the 1st 1000 miles.

[Sean]

I pretty much did what James said. Did TONS of mountain runs (just to break it in) slowly worked up my way to redline, finally hit redline around 400 miles I think. I change my oil at 50 miles, and at like 200 I think. Then finally switch to synthetic at 500. Up until the sythetic, I always had it in a lower gear when slowing down, to help seat the rings.

Feel strong today! But, I'll always wonder if it coulda been stronger. :) I saw so many different opinions too, but I felt the most comfy with this method.

[Court M3]

from s14.net. tons of info for breaking in a rebuilt s14 ;)

".....Oil. 10w-30 mineral (like a Castrol Type in the States). Start and warm up until the oil temp reaches the first white line (150deg.) Starting at this point push the engine from 2000 to 4000 at full throttle. Keep doing this, coasting back to 2000 each time. This should continue for 15 minutes. Every 15 minutes move up 500 rpm until you get to 6000. This should be followed by a drive for 100 miles or so. All this done at one time; no shut down and cool off......"

[nando]

Thanks guys. It's got roughly 300 miles since the rebuild and he's been getting on it, but not bringing it over 6k or so. I think it's time for an oil change and a run down Canyon Road to Yakima. It's just starting to get nice here too.

Too bad he's got the snows on it still though...

I autox'd my engine with a bit over 300 miles on it. it should be broken in by this point - drive it like you stole it :)

I've done both methods - driving it hard from the get go with my M20 (but avoiding extended periods of high RPM), and driving it easy for ~500 miles with a V8 I built years ago. driving it hard worked better by far.