how to break in rebuilt motor???

[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.

[jlevie]

What about specific break in oil?

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

[red_e30]

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

[Mlarsen]

What about specific break in oil?

[delatlanta1281]

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

[reelizmpro]

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

[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]

If that's what Jim Rowe says then I would follow his lead. Good to know I wasn't too far off. I researched this after rebuilding my engine and there are definitely a few different camps out there.

[Cabriolet]

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.

[acolella76]

I was literally just about to post a thread asking how to break in my newly rebuilt M20. Thanks OP and nando!

[JasonC]

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

[nando]

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. :)

[jlevie]

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.

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.

[nando]

Fire up the engine and allow it to reach normal operating temperature. Then bring the engine to 2500rpm and hold it there for 30 minutes. The engine is now broken in. Change the oil & filter and drive the car normally.

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.

[devon.818]

Fire up the engine and allow it to reach normal operating temperature. Then bring the engine to 2500rpm and hold it there for 30 minutes. The engine is now broken in. Change the oil & filter and drive the car normally.

Pretty similar to the little nitro rc cars then huh?


Cool beans