How many miles would you run an M42 after it was beeing rebuild, until reving it

[bmwman91]

I dont know what to think of all this, because everyone tells something different.
Starting about oil that is best on an M42.
Ok, I heard it all, from 0w40 to 20w50, or maybe just put ATF in?
Now on engine break.
Here it seems the same.
Some say, dont go higher than 4000RPM before you have reached 1200 miles, never.
Then, I heard people saying, push it to the limit almost, after a few miles.

Seriously. :loco:
Now I can choose which person I want to belive.

I too have heard a million different things. Which one is the perfect one? No idea. In my case, I just went with what the professional engine builders said to with their engine. I think that generally, running non-synthetic oil during break in and not red-lining it for the first 500-1000 miles are the only real rules.

If you broke it in with synthetic and it runs well/good compression/no burning oil, then you are very lucky. A lot of horror stories can be found on various forums about people using synthetic oil for break in and never having the rings seat properly. Synthetic oil is great for a broken in motor since it offers a lot of protection, but you actually want material wear to seat the rings.

Anyway, if it runs well, don't worry about it.

[nando]

it's not so much that you don't want to redline it. it's that you don't want to stay at high RPM for extended periods of time.

it's one thing to tag the limiter in 1st and 2nd gear, but hitting the limiter in 3rd or 4th gear takes a lot longer which means you're spending more time at high RPM and increasing the risk that the rings will overheat and glaze over before they've seated properly.

on the other hand if you drive too lazily the rings may never seat at all and the engine will not realize it's full potential.

[M3Philipp]

What is the meaning of glaze when it comes to the piston rings.
I am german and I dont understand the meaning of that.

[nando]

the surfaces become smooth and the rings never take shape to the cylinder walls, so they don't seal as well. you end up with lower compression, blow by, oil burning, and less power.

[jlevie]

An oil with a high ZDDP level is good for breaking in an engine. I normally use Brad Penn, but Valvoline VR1 is also good.

The way we break in a race engine is to bring the engine up to normal operating temperature. Then get the engine to 2500rpm and hold it there 20-30 minutes. The engine is broken in at that point. We take the cars straight from there to race track.

[TobyB]

Oh- if your engine is built by someone else, do what they say. To the letter.

Otherwise, well... warantee void!

Since we're sharing ;) I actually try to build bottom ends and heads separately any more.
Then there's no danger of hurting the cam or valves when you stand on it for the rings
(and the cam's already mated to the lifters)
and you can give the cam the gentle break- in with synthetic and ZDDP that Jim describes.
The big problem (M10's and 20's more than 40-50's) are the rockers- they need a lot of
slip to keep them from galling in the first few minutes, but that same slip will let the rings
polish the bores without lapping for best seal...

Way more than you needed,

t

[Massimo]

An oil with a high ZDDP level is good for breaking in an engine. I normally use Brad Penn, but Valvoline VR1 is also good.

The way we break in a race engine is to bring the engine up to normal operating temperature. Then get the engine to 2500rpm and hold it there 20-30 minutes. The engine is broken in at that point. We take the cars straight from there to race track.

How do you tune I have heard/read of race engines going strait from the shop to the dyno to be tuned. They start at 50% load and at about 2000rpm in 500rpm increments and work their way up from there. They say due to the time it takes the engine to be tuned by the time you get up to the higher end the rings are seated.

[///M42 sport]

bringing this back from the dead

Currently have a rebuilt m42 and looks like the breakin oils come in SAE30 or the royal purple 10w-30. If I go with the amsoil SAE30, not sure how thats gonna work if its winter here with temps in the 10-32 degrees F

[varg]

Old thread, but since it's here now... In the aviation world, break in is always done with non synthetic oil at moderate to high power settings, with the logic behind that being that the rings are forced outward by higher cylinder pressures and seat better and faster because of this. Now the engines are quite different than an M42, as are the operation envelopes, but the basic principles and physics are the same so it should apply. The soft break in recommendation for car and bike engines has never made sense to me because of that, unless I look at it as a CYA policy since the average new car driver knows nothing more about a car than what it looks like and the average pilot knows just enough to get by safely. As for breaking in in the cold, proper operating temperature is important, so as long as your car reaches operating temperature fast like it should and stays there, and the ground isn't too slick for a proper loaded break in, I think it should be fine.