Sorry this is a bit of a late post, been in egypt for the last week, and the pyramids havent been fitted out with wifi yet [
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theres three important functions that running in an engine provides...
1) remove small surface defects from cylinder bores, bearing surfaces, valve guides, etc. at lower speeds
2) bed in bearings, rings, gaskets, etc. at lower pressures/speeds
3) lubricate and penetrate all the nooks and crannies and plump-up any rubber seals; this is important as dry seals crack and small spaces harbour contamination and machining debris
Theres one thing thats critical to all three functions and often overlooked... OIL!!!
Hopefully your engine builder gave you an idea of 1st and 2nd oil-change period, and will have filled the engine with "running in" oil. This is typically thinner (however modern fully synth oils like castrol edge are getting very thin now anyway) and helps with all 3 functions; penetrating components, seals, flushing out debris, and reducing load on the engine. This also effects cooling in aircooled engines, so you need to be a bit careful with that side of things too, hence on air cooled engines Ive re-built in the past (mostly VW's) Ive used a thin standard oil like 0W30..
The change periods should be fairly short. I would typically use 500 miles and 1000 miles as the first two change periods, so you've covered 500 miles at lower speeds/throttle openings on something like 0W oil, then another 1000 at slightly higher engine speeds with the occasional blast upto say 4,500 - 5,000rpm adn towards the end some full throttle runs although not from low engine speeds so as to keep the loads a bit lower. For this 1000 miles I would run something like 5w oil, then switch to the oil you intend to run with the car day-to-day (10w40 or whatever). When you change the oil use decent filters!.. This part of running the vehicle in is a clean-up operation, and the filter quality/grade is as important as the oil; if it doesnt catch 1/2 the small particulates, its not worth it.. Considering the costs involved with the filters Id use OEM genuine parts for piece of mind
Even though the engines been re-built, and assuming you havent had all of the anciliaries like oil pump/cooler/lines, etc replaced, I would use an oil suited to higer mileage engines once running in is completed. This will help out the oil pump and the cooling side of the oil system by maintaining decent oil pressure. If you have had all of these parts replaced, it might be that you want to run a thinner oil but I wouldnt use a "new engine" oil as it will be a bit thin still
End of the day, and assuming your engine was rebuilt with a waranty/guarantee of some sort, I would go back to the people who did it and ask their advice; last thing you want is to have a problem and them not honour the guarantee because you didnt follow their prefered running in procedures [
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Ridiculously long post, and probably a bit after the fact.. sorry for taking up so much space and if you made it this far, go get your self a beer and have a lie down [
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ben
PS.. I worked for a race engines company in Oxford building engines for touring cars and Lemans cars. They were never "run in" as such, however the level of machining and component matching that went on was un believeable compared with a production car or an engine re-build in a normal garage/shop. Polising sealing faces on blocks and heads for instance might take a couple of days for one engine, or the best part of a week for an engine with multiple heads. The engines then undergo a "hard run in" process, currently used by honda on their superbikes and type-r cars.. The factory and then the dealer basically thrash the tits off the engine for about 20 miles from new, then it goes out to the customer. The thinking behind that is it knocks all the lumps off and pressurizes everything quickly... personally i think its asking for trouble; see important function 3!
PPS.. Agree with others views, keep the revs between 2,000 and 3,500rpm; dont over-rev the engine, but dont make it labour either; this increases pressures on bearings and things which need time to bed in and settle
