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Letting an Engine Sit

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I'm planning on starting my first engine build and want to take my time with the project. How long can an engine sit in general prior to initiating the break in process? To put it simply, if I build an engine, will leaving it for, say, 6 months before I do the swap be bad for the engine?

Suppose the question is whether the assembly lube will stay in place long enough to be of use? Also if there is a way to effectively pre-charge / lube the engine before it's turned over.

Those are essentially the questions I'm asking, however, I'm also concerned about surface rust developing on the interior of the engine. If you start an engine that has developed surface rust from sitting, could this damage the engine, or will the surface rust simply wear away from the break-in period?

Assembly lube will not magically disappear. It's viscosity is such that it will survive probably for years. As for pre-lubing -- on engines with dry-sumps and external oil pumps, its very common to remove the oil pump drive belt and spin the pump (using a drill motor) to build oil pressure before cranking an engine that has been sitting for a while.

If you don't have access to the oil pump, then another technique is to remove the spark plugs, and spin the engine on the starter until it builds oil pressure. Then re-installed the plugs and fire it up for the first time.

Regarding surface rust.... Engines running alcohol are often pickled (run on gasoline) prior to being stored for long periods. You can spray an oil fog into the spark plug to prevent rust. You shouldn't need to do that with a newly assembled engine, but you could to provide an extra margin against corrosion.

I think if I was given an engine that has rust in the cylinders (from a borescope inspection), I would probably remove the head/pan and check the condition before attempting to turn it over. But I'm sure plenty of junkyard engines just get installed and started right up. But that's not a performance engine.

Thanks for the info! This is exactly the kind of info I was looking for.

When I leave mine for prolonged periods I remove the crank sensor and crank for a few seconds before reconnecting and firing up. Its just much easier for me than removing the plugs


the point is to not have compression.

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