Running In A Rebuilt Engine

[phee]

This is a very controversial topic!!

Tomorrow or the morning after is D day, and then comes the important issue of breaking in the motor. I have heard numerous ways on how to break in an engine correctly, and I have been given a few sites to read here and here.

I have heard leaving it idle for 4 hours will do it, after 20 mins of normal driving is enough and then city driving for 1000kms is what it takes.

How I was going to run it in, is get 300 - 400kms of city driving on her, then head down the highway sitting on different rev ranges for a period of time. (ie - 4th @ 4000rpm for 10 mins, 4th @ 3000rpm for 10 mins, 4th @ 2000rpm for 10 mins same through 5th, then 3rd, then back to 4th so on)

Is this wrong? What are people's opinions on how to run in an engine?

[gts4diehard]

Hi,

With the engines I've done for myself(Fords) and with my Dad (BMWs, Fords,Holdens). These engines were complete rebuilds - pistons, bearings, valve grinds, cam and crank grinds if necessary etc. everything was in new condition.

We always made sure when running in that:

1) the engines didn't sit at a constant rev

2) you don't make it labour in too high a gear

3) you don't redline it.

But don't 'granny' it either, we did this for about a 1000kms. Needless to say the engines ran strong and gave many years of good service.

Really it comes down to just driving an engine normally (without abuse) except you avoid constant revs. I used to take my cars down to some nearby hills about 15 kms away and make the first real drives under a bit of load and use the gears without hitting the redline.

As you have found there are as many opinions about running an engine in as there are about engine oils.

I think there seems to be a more agressive attitude to running in engines these days, still staying away from labouring and constant revs but giving the engine a bit more of a work out. I think this is due to more engines being performance oriented and using better quality metals that need more agressive running in to bed the parts in .e.g. the chrome content of the rings and type of pistons - cast, forged etc. I would check out the sites from the piston/ring/bearing manufacturers you used to ensure you know about any special treatment their components may require in running in.

I don't think the idling method is a good one - constant revs for a start and because it may be running a bit rich and you may overheat the engine - additional running in friction and no air flow.

Edited October 8, 2006 by gts4diehard

[MMM]

yeah what he said

[Abo Bob]

controversial yes. but I agree also with the above. I ran mine similar to that for 1000kms then gradually upped the revs. You will find it feels tight the first few thousand kms. As it frees up you rev it harder until it doesn't feel restricted at high rpm then it's done.

[DEVO R33GTR]

Hi Phee

You should ask the person building your engine how would they like it to be run in and then that covers any warranty issues if they arise.

[benm]

I guess its like engine oils.... everyone has their own likes for their own reasons and will argue those reasons to the death over other peoples opinions.

[342Four]

i have not run in an engine myself so i couldn't say from first hand, but from what ive read, cams do not need to be 'broken in' on modern engines, primarily it is the rings that needed to be beded (spelling?) in.regarding HOW to do that, well, theres a lot of diff methods

here is one from a street commo mag (and i no there diff engines one being OHV and the other DOHC):

a decent quality oil is used, engine under light loads for 20min to check for oil leaks.

after that varying revs between 2500-3500 rpm for a while (will depend and when boost comes on tho) to see that it is performing up to scratch and then the engine is loaded up to bed the rings

after half an hour on the dyno (engine dyno) the oil is dumped, regular oil is put in and the engine should be ready to go

re oils: some say that a prime for 20 minutes with a cheapy semi synth oil to get rid of any garbage that may have got in (very very fine crap, dust) and too check for oil leaks is a good idea, then dump oil and put a fresh filter in then fill with a decent oil of ur choice to use for 2000-2500kms or so (while bedding rings and stuff, and getting engine up to scratch), then ur free to use ur regular oil after that

like ben said, there are varying methods to run it in, just like there are various different oils u can use for ur engine and there are pros and cons for both

the general method seems to be to run for 20 min to check for leaks and stuff, then under various loads to check up to scratch, then bed the rings in.

Edited October 8, 2006 by usherly

[`nigno]

Hi,

We always made sure when running in that:

1) the engines didn't sit at a constant rev

2) you don't make it labour in too high a gear

3) you don't redline it.

But don't 'granny' it either, we did this for about a 1000kms. Needless to say the engines ran strong and gave many years of good service.

Really it comes down to just driving an engine normally (without abuse) except you avoid constant revs. I used to take my cars down to some nearby hills about 15 kms away and make the first real drives under a bit of load and use the gears without hitting the redline.

Thats pretty much spot on what I have followed for all of the rebuilt engines I have handled in my time and never had any problems.

[Kinks]

idling an engine for an extended period of time isn't good for it. oil pressure is low, combustion pressure is low, heat output is low so it spends a LONG time getting up to temp.

just don't flog it (redline), labour it (flat throttle at 1500RPM) or sit on constant revs on the freeway. drive it as you normally would - run standard boost and give it a bit of a squirt up to 5000RPM. combustion pressure helps seal the rings against the bores!!

but at the same time friction will be highest in a new motor so I wouldn't feel sympathetic by forcing it to do high RPMs.

[phee]

It wont only be on idle while it warms up, about 5 mins. Is this too long?

[benm]

Probably a silly question but im guessing when a rebuilt engine is installed back into the car that you then tow your car to the dyno tuner because for some people that could be a 50km drive which could destroy the engine due to wrong tune or driving incorrectly.

?

[ossie_21]

I also get my car back this week, can we go to bed together??

I've been told the rev limiter will be put down to 4000 for the first 1000kms, I haven't had a chance to really speak to him about it but from what I've managed to find out is also like the post gts4diehard made, although in the forced induction section r31Nismoid said get the rings bedded in on the dyno & from there it was good to go!! I didn't think it would be like that but also as mentioned ask the builder what the most effective way will be.

And I'm not sure of the factor it would play but the heat up in the Northern Teritory could make a difference too.....

[RT33]

i just had my engine rebuilt. i've done about 1400kms. i've been varying revs for the the first 1000 not going over 5k. i've been going to 6 once in a while it feels real smooth and feels like it has a lot of power. is it ok to rev it to 7 again? just not hit redline?

thanks abo bob for the 26rods!