Bedding In / Running In A Re-build

[maccattack]

Hi all, Just looking for a bit of input on running in a new (re-built ) engine. There seems to be a fair amount of variation on the most appropriate method for running in. All seem to agree on running a low friction coefficient oil (generally mineral) to start with, to allow the bore to be scraped down without glazing, then changing to a better quality (syn or semi-syn) after the first oil change.

Some advocate short run in times - ie: 2-3 controlled dyno runs and your right to go. Others advise on taking around 2000-3000 klms of restricted RPM's and heaps of engine loading and rev variation along the way. I know you have to be careful not to glaze the bore otherwise you can end up losing power through blow by.

Anyone who has run in an engine - how did you go about it and what where the results?

Thanks

[R31Heaven]

The info you have is spot on, I used to race Go-Karts and the principals are the same, Just use very cheap crappy mineral oil the cheaper the better this will make the rings bed into the bore and give a good seal, and if not using a Dyno to run in Just vairy your Revs used around town startin off by not going over 3000 to 4000rpm for the first 100ks. do not run it in by cruising there must be constant variation in revs.

[boostn32]

very good thread, i also want to know how to run an engine in properly. is it any different with forged pistons than standard pistons.

[Busky2k]

I wouldnt use 'the cheapest oil you can buy' but rather something like GTX3 or something. Who wants deposits and shit in your engine from running back yard oil...

[maccattack]

From what I understand though, is that it needs to be shit first up. You actually want the rings to "scrape" the walls and take off the minute score marks from boring and to "bed" with the walls. This is then drained after a relatively short amount of time and all of the associated crap is drained away with it. If the oil is too good, the rings will simply "slide" against the bore wall and eventiually glaze up. This will produce a poor seal and you will loose compression.

The point is however, which is the BEST method of bedding an engine - quick or slow??

[Bobjones]

Alright this is what my engine builder told me and is also what my dad and his mates (one who is 3 time National Pro Stock champ who built his own engines) has confirmed.

Note: This will vary from engine to engine, ring type to ring type and application to application.

Engine: RB25DET, Chrome-Moly rings and forged pistons (Venolia) unsure of exact clearances but pretty tight as on cold it will generate 4-6kgm2 below 3000rpm when cold on 5-40 Pennzoil full syn.

Run in procedure:

First 100km, use proper full mineral run in oil, vary revs keep loads up do not exceed 3,000rpm, ie keep it off boost as this helps the bed in and reduces the change of bore glaze. During this time I also disconnected the turbo timer just in case. The hone on the bores was also reasonably rough/deep compared to stock hone as we were using the moly rings. Drop oil and change filter

First 100-1000km's repeat process above.

1001km - 3000km - this step is not really necessary, however depending on clearances, tollerances ring squish etc may be helpful in an exellent bed in and further reduces the chance of blow buy and poor piston bore bedding. Drop oil and change filter. Another option is semi-synthetic, something like Motul 4100 turbolight 10-40 would be ideal if using standard rings or non-moly ones.

3000km, at this time I went for a semi-synthetic at this stage however, if you have done this between the 1001 and 3000km range then go to a full synthetic or maintain the usual oil changes on the semi. Depends on the engine builder's recommendations.

3001-5000km, changed to full synthetic Pennzoil 5-40 (I think it may be 5-50) upon recommendation from the engine builder. All cylinders have compression within a range of 5-7psi difference depending on gauge, perfectly bedded in and runs like an absolute dream!!

The additional point I want to make is...

IF YOU ENGINE BUILDER CANNOT RECOMMEND A RUN IN PROCESS, FIND ANOTHER ENGINE BUILDER!!!!!!!

On another note, street engines have always been run in a longer process than a race engine, these or often done on the dyno but involve just as many oil changes!!!

[maccattack]

Thanks Bobjones,

Pretty much what my mechanic had told me however I have been reading a number of articles about faster bedding methods (which the authors claim - work like a charm every time). As I do monthly track work in my car and have been waiting patiently for the build to be complete - I am rather impatient and want to get back onto the track as soon as spossible. Similarly, I have been driving around in a piece of sh1t for about 6 weeks now and can't wait to find out how the mods made during the build feel at full noise. In saying that - I don't wan't to stuff all the good work of a full re-build by going about bedding the engine the wrong way. Perhaps I have been looking for the "magic wand" method - which will get me back into it immediately. Patience is a virtue they say.

[R31Nismoid]

mine was a case of bed the rings on the dyno.

tune it up and off i went... service after 1,000km's just to make sure its working fine.

Motor never had a problem, 10,000kms on still fine.

[Bobjones]

As I said it depends on the build of the motor, R31Nismoid I am sure you did that on the advise of the builder??

I have also run engines in on the dyno, but usually with two oil changes atleast, assists the process.

I have also seen 15K plus builds go up in smoke on a dyno run in....

There are alot of factors that need to be considered, by merely saying hey mine was done on the dyno and its fine after 10,000km's does not prove a damn thing...sorry

Edited August 19, 2005 by Bobjones

[R31Nismoid]

As I said it depends on the build of the motor, R31Nismoid I am sure you did that on the advise of the builder??

That was the builders advice.

Considering the motors that come out of this workshop.

I dont aruge... and no-one else ever does either

As for what it proves... well. Most people say it wont make power, have huge blowby etc etc. List em all i cbf'd doing as ive gone into it before.

Because its against the common thinking people cant accept it.

If the motor makes the same power it did 10,000kms later its a good sign there is nothing wrong. Which i think is proof in itself.

Motor comes apart shortly for inspection before sale. I expect to find everything A1

[Sydneykid]

As many have said, running in really depends on how the engine was built. What tolerances the engine builder used, what materials where used, hone on the bore etc. Simplistically bearings don't need running in these days, they are fit to run out of the box. So there are really only 2 things that require a run in period.

#1. I call this clean out, bascially it involves making sure any dirt, machinings, gasket goo etc are cleaned out of the engine. That is why we change the oil filter after 5k's or so. This takes anything that the filter picks up out, leaving no possibility of it sneaking back into the engine. It isn't necessary to change the oil at this stage, but some people do. I use 100% mineral oil, something like the basic Castrol GTX, it's cheap and easy to get anywhere (handy for top ups).

#2. Rings, this is the vital part of any engine run in, particularly a turbo engine. They need mixed loadings, never full throttle, high rpm or high boost. Long up hill runs are good, where you can load the engine up with a bit of throttle and hold speed but vary the load. I find the run to Goulburn and back is great, it has all the mixed conditions.

At the same time as I do step #1 (at 50k's) I check the A/F ratios on the dyno. It takes about 10 minutes, but I make sure that it is neither too lean (detonation risk) or too rich (patchy run in of the rings). It costs like $50, and from other posts on the forum you can see why I reckon it is compulsory.

After step #2 I do a leak down test, I am looking for over 90%, preferably over 95%. If I don't get that, then I do another run, maybe over the Blue Mountains to Bathurst, plenty of variable loads there. When I do get a good enough leak down test, I change the oil (to Castrol Formual R Synthetic) and oil filter. Then it's onto the dyno for a proper tune.

cheers