Oil Galley plugs at Camshaft

Needswork said

I took my own advice on my suggestion to YR. I'm working on my own stroker 340 and was doing some test fitting of parts and such. I went ahead and bolted on my oil pump, pan, added some oil and spun the oil pump with a drill. This is with NO galley plugs, just the cam plate (4 bolts). With 5-30 oil and 50 psi on the mechanical gauge I hooked up, there was only a small amount of oil escaping behind the cam plate. It didn't make a big mess like I expected (or remembered from the past). Instead, it just dribbles down the front of the block. My guess is maybe 1 cup of oil a minute. Other setups might be different. A plate with only 3 bolts might "leak" more. Just my experience. I'm still going to install the plugs.

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Thanks for doing this; it is some extra work and I appreciate the effort.. very much! But there is a matter that is making the resulting leakage quite misleading.... the oil is not hot and so the viscosity is waaay off. Kinematic viscosity for that 5W30 oil will be around 80 at room temp, and around 60 at 100F, but the viscosity will drop like a rock to around 10 at 200 degrees F. So such leak tests are not valid with the viscosity that far off from actual operating conditions. Folks don't fully appreciate the extent of the viscosity changes as temps go down.

As an example of what you have to do to simulate this properly: I am preparing for some oil pump pressure and flow tests on another engine, and to simulate a hot 10W40 or 20W50 engine oil with the test oil at 100F, I have to use a 2.5W shock oil to get the same kinematic viscosity number. (There is no motor oil type or grade out there that will have the proper viscosity at 100F for my tests.)

So if you want to see what the leak really is with the oil hot, then get a few quarts of Motul 2.5W Expert fork oil and see what you get. Even then, that oil's viscosity is not quite as low as that 5W30 will be at 200F, but you will be a lot closer.