Run in verus Break in

Two conflicts on new engines, seat rings and burnish in cam/lifter interface. Rings like it dry and short high loads then cool off to knock off machine ridges before getting so hot it smears galls. Cams like it hot and fast for oil wedge.

Jim Comstock summarizes the cam side, the main issue as rings usually seat well in a few seconds to minutes.

To the original question, the oiling scheme relies on the flow capacity of the scavenge side being greater than the supply side, which is set by the relative width of the gears - there are four gears. all the same diameter, with the two scavenge gears being wider than the two supply gears (brilliantly simple way of assuring scavenge). The oil level in the sump is set by the position of the intake. Since the scavenge side has more capacity than the supply side, the oil level in the sump falls until the intake sucks air, then it stops falling (also a brilliantly simple level control scheme). Thus under normal conditions there will always be bubbles in the return line to the tank, which serves to enable the air to separate from the oil as well as to radiate some heat. And as has been pointed out in another thread, the pressure at any point in the supply side of the system - or return side, for that matter - is set by the flow resistance existing there. Pressure really only matters for the plain rod bearings, which require enough pressure somewhere upstream to ensure flow to replace the oil squished out every rotation of the crankshaft, otherwise the surfaces touch (and no, the oil pressure doesn't keep the surfaces apart, the hydrodynamic wedge inside the journal does). In the roller main bearings, the roller and race surfaces normally touch - well, there is the film strength to keep them microscopically apart - and the oil serves to reduce the friction and temperature associated with that - thus they just need to be kept wet (but not submerged, because that would cause too much viscous drag and froth etc.) and the heat get rejected somewhere. The top end is basically the same story as the mains.

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That hydrodynamic wedge is why I harp about people cranking a new motor until oil pressure comes up. Just like a car tire on a wet highway surface speed is needed to keep the two surfaces from contact. According to formulas from some old sae papers that speed is around 1500-2000 rpm to keep a Norton lifter from intimate contact with the cam. It depends on the particular oil, the spring rate and surface finish of the parts. [along with contact area, radius and a lot of other things]
A newly machined part has no surface protection until the part has been used. Pouring oil over the part doesn't do it. The metals and other additives in the oil get burnished or baked onto the metal part when it is in operation which will then provide some protection. Until that has happened the surfaces are prone to scuffing from metal to metal contact. That is why cam manufacturers tell you to bring the engine up to speed as soon as it is started. The speed creates a hydrodynamic wedge that keeps the parts from touching.
The lube that comes with a cam is primarily to provide protection for a few revolutions so you can get the engine assembled and started. Some cams use a deposited layer such a parkerizing which provides protection for a little longer.
The same thing applies to any non-roller bearing in the engine. Jim[/quote]

My solution, especially on Ms Peel with all sorts of questions to even get started let alone run to matter is same ideal place I do plug chops. I run hard up it cut power and clutch then coast back and look diddle and repeat. Its a
Steep 11% grade 1/4 mile long with a truck brake check cooling park area at bottom. So plan is haul to site, get rolling start drop clutch to spin engine 1800+ then hit key and hang on 'hi' throttle then cut power and coast down, fiddle with what ever, then haul back and repeat till rings seat and tuned enough to just ride over 2000 rpms on way home and done with it. Photo of site later.