Running in

[timbigden@icloud.com]

Further to my last post - I have rebuilt my engine with modern internals (crank, rods, slipper pistons & new rings, new std valves) the block has also been rebored. What running in regime is recommended?
TIA.

[Hugh Barnes]

Oil is cheap compared with the cost of the new engine. I do my first oil change at 15 miles, then at 50, then at 100, then at 150/200 and then slow down the frequency. Subjectively, this has lead to engines running on much less contaminated oil going forward. I am somewhat less concerned about speed as long as the engine does not labour. Though don't thrash it, clearly...

My regime - other regimes are available, I am sure...

[Ian Williams]

Pretty much spot on in my experience Hugh, I would add, don't over nurse the engine or you will not bed the rings in, it needs to be loaded and engine speed varied but not over revved as Hugh mentioned.

[Chris KC]

My own approach is similar. I use an in-line oil filter & admit I'm not quite so fastidious about oil changing.
First runs should be very short, watch the temperature. Then go around the block a few times - my thinking here is mainly to be within pushing distance should it conk out for some reason (nobody's perfect...)
Re-torque the head nuts when the engine's cold (and keep doing so till nothing moves).
Then as confidence increases make longer and longer runs, carrying a tool kit.
I have a favourite small road I use for this - there's no traffic, plenty of bends and modest hills, and I can follow it through countryside for a couple of hours and end up at a place which sells tea and bacon butties. You don't want to be fighting to keep up with traffic. You do want to be working the engine, very gently at first, but as you feel it start to loosen up after a few hundred miles start to work it a little harder. Short periods of exertion followed by gentle cruising & repeat.
High revs should be avoided until you have at least a thousand or more miles covered, but I'd far sooner rev the engine than labour it in a high gear, which is to be avoided at all costs (even after you are run in).

[Colin Bromley]

I have never had any running in procedure, other than changing the oil after the first 50 miles, I just fire engines up and use them normally. Rings need to bed in, they like load to do this, so pottering around will not do it much good.
My daily car is a 2CV which has had several engines over the years, these are normally assembled and fitted in a weekend, and then used for going to work on Monday morning.

[Steve kay]

What we were taught when I were a lad, was first to turn it over with plugs out for a few minutes to ensure that oil galleries and relevant pipes were full, then check oil level in the sump. After that, do not just warm it up or let it tick over, otherwise everything would be as glazed as a helping of carrots in a gastro pub pretending to be NC. Use it. Oil change after about 50, another change after about 100 and carefully inspect the oil each time. Use it.

[John Cornforth]

Hi

After a recent top end rebuild with modern slipper pistons and new rings, I found that turning over on the handle there was plenty of compression "spring" but pleasantly surprised to find reduced frictional drag compared to the previous pistons. The 6V starter motor now turns vigorously. I followed a typical run-in procedure as advised above of normal road usage and frequent oil changes, but there was no noticeable tightness - the main problem was avoiding the temptation to use too many revs. Right from the outset oil consumption has halved compared to the previous setup.