Hi, Fred A very interesting treatise on this very important exercise on a new or fully rebuilt engine. It seems techniques are changing and this makes me wonder if they have come about with modern engines and their tighter engineering tolerances with consequentially higher operating pressures. Whatever the reason and the undeniable developments over the last thirty years on lubricant quality - the bedding in process should not be rushed.
For comparative purposes, it may be of interest to listers to know the procedures employed Standard-Triumph in breaking in all company cars, especially the Press cars and those that were broken-in for customers on the Personal Export Scheme. This was normally done over the course of a weekend during which time the car was driven for its first 1000 miles. We had several routes in the UK that were carefully developed and were a combination of town driving, open roads (not freeways) and fairly demanding hill country. On Spitfires, for the first 500 miles, engine revs were kept to no more than 3000 in any gear, with gentle acceleration and gradually building up to 4500 providing the engine was on over-run - like in descending a hill. For cars without rev counters, road speeds were limited to 50mph, slowly building to no more than 65mph for short periods. We never allowed engines to idle while building up to operating temperature as a lot of the critical friction reduction of high spots on bearing surfaces was achieved while the unit was cold. From 500 to 1000 miles, the rev band was progressively increased to 3750 in direct fourth gear with very brief forays to 4500 without load and the engine was always allowed to rev more freely on a very light throttle. The 1000 mile service obviously involved draining off water-absorbing oil, a full release of cylinder head and manifolds, followed by a full re-torque and re-setting of valves clearances. We found from regular engine stripdowns by Engineering that this extensive mileage in a very short time period maintained optimum engine coolant and oil temps for prolonged periods and these were the best environments for progressive bedding in of related friction surfaces. Allowing the engine to rev freely but not hard was favourable and while 1000 miles was something of a threshold, engines rarely started to really give of their best until at least 5000 miles had been covered. I have many memories of undertaking these trips and the abiding memory is of engines that were supremely supple, free-spinning and economical. They compared far more favourably to those which had been broken-in on short journeys which still felt tight, unwilling and rather unresponsive. I've always employed these techniques with new cars of my own in the years that followed and the current 1400cc Eurobox is shortly to turn 200,000 miles. The head and bottom end has never been removed, compression pressures are still within factory limits, though I'll be coming up for the third clutch within six months and synchro between 1st and 2nd is now weak when cold. As a tip, I've always used magnetic plugs in the engine and gearbox and never cease to be amazed at the amount of ultra-fine swarf and metallic paste they attract. It goes without saying that there is no substitute for regular oil and filter changes and to run the engine on clean oil as often as you can afford to change it. 3000 miles is my limit. I suppose the bottom line here is personal preference but I'm convinced a good break-in and prolonged engine life comes from a relatively constant speed in the very early days, a light load, constant operating temps as long as possible and an absence of severe load under hard acceleration. It will be interesting to see how others view this important aspect of an engine's early life. Cheers, Jonmac 1950 Ferguson TED20 152318 - Grey/Grey 1970 Triumph 2.5PI MG4305DL(O) - Sienna/Tan 1974 Triumph 2000 ML2294DLO - Mallard/Black /// [EMAIL PROTECTED] mailing list /// Send admin requests to [EMAIL PROTECTED] /// or try http://www.team.net/cgi-bin/majorcool /// Archives at http://www.team.net/archive /// Send list postings to [EMAIL PROTECTED] /// Edit your replies! If they include this trailer, they will NOT be sent.
