Breaking in a rebuilt engine.

[keltik]

Factory motors are usually assembled to much better tolerances with better fitting parts than mr average joe. Plus everything is new and rings dont have to contend with partially worn bores and metallurgical differences from years of heat cylces and contamination.

Ive never had to run in an engine before so i have no opinion. Actually i lie, i ran in a few 2smoke outboards for my old man. Procedure was always the same. Run at 75% rpm, max load. The common denominator seems to be lots of load but not max rpm and no lazy idling or cruise.

[CaMpylobacter]

'start as you intend to continue' is what i've always been told. thus, drive it like it's meant to be driven. don't be a nana.

running in oil IMO is a waste of time. you're not dealing with white metal beairngs that are hadn scraped anymore. jsut make sure it's a nice plain jane mineral oil. get the load into it asap, without treating it badly.

factory engines probably do a few hours on an engine dyno for running in.

[fuel]

Breaking in an engine seems just like choosing an engine oil.

Everyone's method is divergent not inclusive.

As in, "I did this and it works fine, therefore its what you should do"

Doesnt mean that doing something else wouldnt have acheived the same result.

What happens to factory new motors?

They dont get any special oil or run in for 1000s of kilometers in a particular way.

What I would be interested to know, is who has run in an engine and then had it FAIL, or glaze the rings or whatever, what were the symptoms, and how was this diagnosed as the issue.

Factory motors do have special oil for the first few thousand kms. That's why they get you to come in for your first 'service' within 5,000kms and they change the oil for free. Many of them have labels somewhere on the engine or oil cap that gets removed at that service stating that it has special oil in it. And the engines get broken in on a test track/dyno long before the average joe gets their hands on their brand new car. By then the engine has already racked up the crucial first few hours and now it just needs to be driven gently.

[Vintage Grumble]

http://www.mototuneusa.com/break_in_secrets.htm

[shavenYak]

http://www.mototuneusa.com/break_in_secrets.htm

The thing about that one though, is it seems to be a newschool method geared towards modern engines:

Several factors make the older information on break-in obsolete.

The biggest factor is that engine manufacturers now use a much finer honing pattern in the cylinders than they once did. This in turn changes the break-in requirements, because as you're about to learn, the window of opportunity for achieving an exceptional ring seal is much smaller with

newer engines than it was with the older "rough honed" engines.

In addition, there is a lot less heat build up in the cylinders from ring friction

due to the finer honing pattern used in modern engines.

The other factors that have changed are the vastly improved metal casting and machining

technologies which are now used. This means that the "wearing in" of the new parts

involves significantly less friction and actual wear than it did in the distant past.

So I'm not sure how relevant it is to an early 80's mitsy engine.

It's not getting done till next weekend now, so I've got plenty of time to receive read up on conflicting points of view.

[pusherman]

put new big ends and rings in my crossflow its bluprinted has a cam nt sure what and twin dellortos, warmed it up i couple of times messing around gettn it right and the first run revved it to 5k in first 2nd and third up the drive way (rural) 2nd run wasnt far different and it continued that way for a week until i felt guilty and took her easyer. feel much better after reading that guide now

[Shandangles]

^ you dont need to run in bearings as (in theory) they dont actually touch anything as they have a layer of oil on/around them. rings are what need running in

[Dell'orto]

Factory motors do have special oil for the first few thousand kms. That's why they get you to come in for your first 'service' within 5,000kms and they change the oil for free

My work car didnt? First oil change was scheduled for 10,000

[davidian]

question re. this: I plan to freshen up my engine soon. however the car isn't wof'd and reg'd and wont be when engine work is done. dont really want to take it for an epic run in without those. is it safe to do a few short to-and-froms (to get the car legal) then run it in? cheers

[Ranter]

I've run in heaps of engines mainly Jappas and old English stuff. I have never used running in oil.

As posted before I just make sure there is nothing wrong like an oil leak or more importantly a air lock in the cooling system, then hit the hills. I also use the brakes to load the engine straight off. I have never had one fail or burn oil (even in massive patch ups) and I can only drive between 20km and 40kms before handing them over to the owners.

Idling is what kills them, running large carbs untuned or similar would also hurt

I have never seen or heard of new engines having running in oil, and have fitted brand new engines before, did nothing different than normal. They don't really do the 500/1000/1500km check anymore, more like 15000/20000km.

[Simon]

Someone asked about new motors:

They come off the production line wet and straight onto a dyno where they are given assholes by robots running a "run in > try kill" program. Just like anything that comes off a production line is tested to beyond it's typical usage.

If one breaks or is not within a certain power deviation they go to the scrap pile. All fully automated as it costs less to make a new motor than it does to pay someone to strip the motor down and find out what was wrong with it, fix it etc.

Toyota make over 35,000 cars per day.

Kinda sad really.

[peteretep]

kills them, running large carbs untuned or similar would also hurt

without being rude, can you actually back this up with anything? Like Roman said, I would also like to know what actually happens if fails, symptoms etc

I remember when me and fuel rebuilt the motor in my galant, he mentioned that someone he knew had not properly primed the oil pump and that it ran the bearings almost instantly

[shavenYak]

oh yeah that reminds me - priming the oil pump. I understood this as filling the oil pump casing with grease (which I have done). Is there more to it? My brother talked about taking the oil relief valve out and filling oil in from that way, but can't see how that would be possible on the 4g63.

[keltik]

From what i know, the grease thing is correct, then once built you just wind it over on the starter with plugs out till you get good pressure.

[Roman]

My motor since being rebuilt has spent a shitload of time idling with no load on it, running stupidly rich, and all sorts of other unsavoury activities.

I took it out for its first good run pretty much straight to the race track, and beat on it till it broke (loose valve guide)

Apart from an error with machining, there were no discernable problems based on having had the engine idling for long periods or otherwise.

Beat on it to redline every gear, synthetic oil.

I've got the head off at the moment, and there's no damagey looking wear patterns on the bore, or anything like that, everything seems fine, despite having done the worst possible thing for a new motor, according to current wisdom.

I guess a compression test would perhaps show the true story though. (Or pulling the pistons out, but CBF)

[Rookie]

What supossedly happens is that the rings don't bed in to the bores as well as they could, and you lose a little bit of compression, and also burn oil. Whether this is what happens in real life is the real question. I guess you would have to build multiple identical engines to find out.

[Dell'orto]

kills them, running large carbs untuned or similar would also hurt

without being rude, can you actually back this up with anything? Like Roman said, I would also like to know what actually happens if fails, symptoms etc

My guess would be having them running excessively rich and bore washing it.

[Ranter]

^Exactly, the old 2e Toyota engine was awesome at it. Carbs were shit at hot starting, they would fill the sump with fuel. People would rebuild em without fixing the cause and the fresh engine would eventually burn oil again or worse. Used to get brand new short blocks from Toyota for $700 and fit a NZ carb with a manual choke.

I've recently done a old Hillman SV, car had not been going since the 60's so I wasn't real happy not being able to do the usual run in + in and out of the workshop each day is not good. The original trip around the block is all it needed.

Its one of those topics, everyone has different ways and opinions, stick to what has worked for you before or take the best of what you have read, I'm just saying don't be afraid to load em up early.

[cubastreet]

Everyone says 'this is definitely the way to do it, that way will wreck your motor',

but surely someone in a shop somewhere has taken two identical brand-new bikes, thrashed one and nannied the other, then done a compression test?

[keltik]

Everyone says 'this is definitely the way to do it, that way will wreck your motor',

but surely someone in a shop somewhere has taken two identical brand-new bikes, thrashed one and nannied the other, then done a compression test?

Yeah but that doesnt answer the question either, since a million and one internet mechanics will say "sure that worked for that particular motor but so-and-so use different castings/clearances/metals/magic that need a different run in"

Everyone seems to agree dont nana it. Id say thats a good place to start and just make the rest up with whatevers convenient.