how to break in rebuilt motor???

[catuned]

All valid points. There is brake in oil additives available made by redline and most imports (ie Honda, Acura, etc) say to use Straight 30 oil for brake in. That is for the 1st oil fill. Then after oil change going to multi level oil.

[nando]

I dunno, I "broke in" my clutch at the same time I was still learning to drive stick and with a brand new motor. It never had a problem.

[brianao34]

Bumping this, I would like to try the website method as it makes more sense, but what about the clutch?
Obviously I'll have a new clutch that'll need to get broken in as well and I've always heard not to get on it hard with a new clutch for the first 500 miles.
Or is it if I just don't drop the clutch?

[Irish1]

Who's building your M20s? I need a shortblock done to replace a bad one from a previous build.

i've only done 4 m20 break ins. so far from expert but i do follow the same steps as nando.
warm up the engine (the gaskets will smoke) at this point i bleed out the coolant system.
then drive her up and down the street for about 30min. take it for a short drive come home and check for leaks. finish driving her like a grandma till i hit 100 miles. change the oil and proceed to drive her like i stole it.

[Dagamus(NM)]

they are likely breaking in a cam at the same time though. that's the exact method you use to break in a cam. And then, they basically race the motor. So you're really not disagreeing with me. :)

This is where it gets confusing. Breaking in the motor as though it is brand new. All head parts brand new, all bottom end parts brand new except reconditioned rods and crank.

Some talk about breaking in the cam, others about the rings. What is the es way to do these simultaneously?

I figure that I will heat up my Torco oil in a large roasting pan in the oven to about 325 degrees then pump it into the motor. Prime the system with the little socket thing I made to spin the pump with my cordless drill for a couple minutes. Bolt the pump hatch shut and start the motor.

Then most likely a mix of freeway loads, wot/ct and again.

Clutch is also new. Should be fun.

[318isbmw]

The nice thing about this subject is that there are lots of "authoritative sources" with different opinions.

I learned the procedure I described from a NASCAR engine builder. He said that they ran the engine like that mounted on a water brake dyno, then tuned engine and tested it. From there it went straight to a race car and was raced. If there was a better way, you can be real sure that they'd use it. As he told me, "10hp is the difference between 1st and last at Daytona.". They'll do anything that they can to wring the last fraction of a horse power out of the engine.

Seating the rings or breaking in the cam is essentially a polishing operation. You want to do it with the parts under the least load. Running the engine at 2500rpm with the car stationary is a minimum load situation.

I learned the same technique for breaking in a rebuilt motor. From a drag racer/ engine builder here locally. He's been doing it for years and I've got a couple motors that he bored and balanced for us that we used the technique on when we did first start up. Also several family members he's built motors for that have lots of miles over the course of 20 or so years with no ring failures as mentioned by nando as a possible issue.

[Dj Buttchug]

I heard once from a master tech that you cant run fully synthetic oils in new engines. specifically GM stuff. The idea was that the synthetic oil creates to much lubrication and prevents the engine from breaking in properly... totally ot but ya. weird

[Aleg]

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

[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.

[e30_neverstock]

interesting.

[Exodus_2pt0]

To prevent dumbasses from constantly redlining the motors and blaming Subaru

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

[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

[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.

[samiam3356]

cya

There's a lot of that in this business.

[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