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Engine oil condition after a few minutes of run time

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After a few minutes of run time, my blown BBC had a creamy tan substance deposited on the underside of the intake manifold. After seeing this, I went ahead and drained the oil. There is a tan substance mixed in with the oil. Could this just be assemby/cam lube or does it look more like coolant. I poured it into a clear plastic container and after a week it is not separating.


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Some assembly lubes do look just like that i.e. Lubriplate. You could ask the builder what they used.

If for example they say they used Redline, Amsoil, Permatex that are bright red, then you'll know otherwise.

I asked the builder and he said he used Clevite Bearing Guard #2800B2 which is bright red. So unless it changes color when it mixes with the oil, it is probably not the assembly lube I am seeing in the oil. I did notice that when I slowly poured the oil back into itself, bubbles would rise to the surface where I poured it in. I tried it on some used motor oil and got no bubbles.

You can send oil samples to specialists and get a full run-down of contaminants, costs a few bucks, but cheap insurance.

You don't mention what fuel you're using - if it's an alcohol based one, you may have fuel mixing with the oil from excess fuelling?

You may have a weeping head gasket, or two, or have a cracked head or block - have you tried a cylinder leakage test?

I sent in an oil sample for analysis but have not received the results.

I am running 87 Octane pump gas right out of the pump.

I have not tried a cylinder leakage test. I thought I would wait until I get the oil analysis.

Did that builder do both the block and the heads?

If two different places did them, perhaps the other one used the creamy white style assembly lube?

Moisture in the system mixed with oil and fuel vapors does also cause a milky white look.

Pragmatically, if your checks don't turn up any issues, after that you may just want to change the oil, run it again for a little bit, then look again and see what you find. If the situation doesn't repeat, it was likely material from assembly that's now out of the system.

I assembled the motor. Two different shops did the machine work on the block and the heads.

As many times as I tried starting the motor, it could have introduced extra fuel. Wouldn"t the fuel evaporate from the oil after some time?

It did backfire a couple of times.


I'm still wondering if one of the two shops applied some lube somewhere you didn't see during your portion of assembly and that's all that's happened here. I'm very hopeful what you've caught is nothing to worry about, but you'll find out soon enough.

Fuel mixed with oil seems to stick around for a very long time.

After letting that oil set for about 2 months, the swirls have almost completely disappeared. That indicates to me that it was probably excess fuel. My plan now is to change the oil and keep an eye on it.

Please keep us posted Jim. Hopefully with fresh oil and some more run time all will be well.

You said you'd sent an oil sample in to be tested, as suggested, what was the result - it's been a while and the assay usually doesn't take much time?

The report contained a detailed list of all the elements that the sample was tested for along with the numerical results and universal averages. Here is their summary report: "Potassium and sodium are coolant markers, and low levels typically rule out coolant. We detected

6,205 ppm of water via the Karl Fischer test, though. It could be from coolant, but it's hard to say since

potassium/sodium are low. Monitor for coolant loss as a precaution. We couldn't get a fuel (flashpoint)

reading due to water. Wear metals and silicon are high next to the universal averages (based on ~2,300

miles), but that's to be expected with a new engine. That extra stuff should wash out over the next few oil

changes. Change this oil, and try ~1,000 miles.

The water problem is a little ambiguous - if it's a drag' engine, it's possibly using pure/distilled water as coolant without any additives to give the coolant markers, but every gallon of fuel produced more than one gallon of water* and it's possible bedding in rings may be allowing moisure past them, especially as the engine will be cold.

*usually in the form of vapour/steam that is passed out the exhaust - it condenses in the exhaust, especially on cold mornings, and can often be seen dripping from the tail-pipe until the system gets hot enough to boil it off.

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