how to break in rebuilt motor???

[ak-]

When the Subaru STi's came out, they told you not to take it past 4rpm for the first thousand miles lol. Reason?

[reelizmpro]

Probably didn't want drivers boosting during break in. From their perspective, it doesn't hurt to play it safe.

[delatlanta1281]

I'm going to do what my piston guy tells me to do.

[Mlarsen]

What about specific break in oil?

[red_e30]

all really good inputs think im going to break it in the hard way:D

[jlevie]

What about specific break in oil?

Use any 20w50 dino oil with a high ZDDP content. VR1 is easy to find and works.

[Wh33lhop]

I basicly do what nando said, but i run it like that for the first 500 miles.

I do what nando said, but I still use 4th and 5th and I drive it like that forever.

[nando]

when the subaru sti's came out, they told you not to take it past 4rpm for the first thousand miles lol. Reason?

cya

[samiam3356]

cya

There's a lot of that in this business.

[e30evolution]

This

I disagree COMPLETELY. that's how you break in a camshaft - not a motor.

the only thing other than a new cam that would need to be broken in are the rings. you don't break in bearings. Rings will glaze over if broken in improperly - and holding a constant RPM for 30 minutes is a good way to do that.

This is what Jim at Metric Mechanic reccomended. He's built a "few" engines over his lifetime I'd say:

-start it up, warm up for a few minutes (checking for leaks, oil pressure, etc).
-Go for a drive. You want to vary load and RPM (full throttle, lift, full throttle, lift). This loads the rings against the hatched surface of the cylinders to seat them. Don't baby the thing - drive it like you stole it, except for two things:
1. Full throttle is fine, but don't stay in high RPMs for long periods of time. That means hard acceleration in 1st, 2nd, and sometimes 3rd gear, but not 4th or 5th. Lift your foot completely off the accelerator.
2. No trying to top out the car.
-As you're driving it, you can increase RPMs more and more each time. 3000, 4000, 5000, 6000, redline, etc.
-By about 100 miles, the engine should be completely broken in. None of this "drive it like a grandma for 1000 miles" crap. :p
-change the oil and filter. Change again at a normal interval. If you built it properly, you won't have crap in your oil anyway. Basically, if there are metal shavings in your oil, something went VERY wrong. Or you didn't clean things when you were putting it together. Changing your oil too early can do damage too - things are dry until the pump starts circulating.

I also don't really buy into the myth that synthetics will cause the rings to have problems but that's another tangent.

Breaking in a motor is fun. Drive the piss out of it, but just don't stay at 6000rpm for 5 minutes. I accidentally redlined my motor in the 1st block - it accelerated in 1st gear a little faster than I expected. It has 60k on it now. :)

I did another motor with the grandma method. It was a dog.

[acolella76]

When the Subaru STi's came out, they told you not to take it past 4rpm for the first thousand miles lol. Reason?

To prevent dumbasses from constantly redlining the motors and blaming Subaru

[Exodus_2pt0]

To prevent dumbasses from constantly redlining the motors and blaming Subaru

Or breaking ring-lands... wait they do that anyway

[e30_neverstock]

interesting.

[Kershaw]

lots of different ways to break in a motor, all claiming to be the best. of course, you cant break in a motor twice and compare the results. so who knows? my moms subaru was owned by an old lady (like her) and she claimed when my mom bought it that it never once went past 3500 rpms. it now has 250k on it and it runs very nicely. clutch last to 180k.

i've heard of nando's way to do it. but im 100% sure jlevie's way to do it is also effective. if nascar teams do it, you know at the very least, that it is not a wrong way to do it.

[Aleg]

I used the website OP posted which is similar to what nando said when I rebuit the s50. Around 10k without problems.