oil viscosity and microinch

I have my rebuild car engine in my toolroom and wonder about how much oil pressure at what viscosity to fill the bearings space. What is "film float" and how to calculate it.

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It's not clear what you're trying to accomplish. If you're trying to "float" the mechanical parts on an oil film (hydrostatic lubrication), that isn't the result of pressure from the oil pump, and no car-engine oil pump is going to accomplish it. The oil flim develops from moving parts sliding relative to each other -- hydrodynamic lubrication.

Are you just trying to lube the engine in preparation for its first run after a rebuild? If so, you just want to make sure there's plenty of oil in the bearings and that the oil pump is fully primed. One way that's done is to pull the distributor and to drive the oil pump with a big variable-speed drill for a half-minute or so, then replace the distributor and fire up the engine quickly.

But that depends on the engine, and how the oil pump is driven.

-- Ed Huntress

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Ed Huntress

Every engine I have rebuilt was assembled with "Lubriplate" or other assembly lube. STP works well also. If youu wait for oil pressure you can damage bearings.

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Tom Gardner

All you need to do is use the same oil that is recommended for the engine on the bearings. Using Lubriplate is not a good idea because any globs of it can plug the oil pump pickup screen. Also lubriplate is very hard to keep clean, not unless you open up an new can/tube everytime and your hands are spotless. Nothing like rubbing a little dirt on the bearings. While using oil use directly from the oil container and just pour a little on. The access will just run off, just the same as when the engine is shut off. Only room for so much oil. Another thing you can do is fill the oil filter with oil too. Prime the engine as mentioned before, by turing the oil pump. If not feasible than crank the engine with ignition off until builds up oil pressure. The little bit of turning and as long as everything was oiled it will not hurt anything. I rebuilt engines for over 20 years from little 4 bangers to heavy duty diesels. Cleaniness is the most importance.

Tom Gardner (nospam) wrote:

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