General question about why some engines seem to make metal and others don't

[PTK]

We have on here instances where seemingly low time engines start making metal while others don't. It has been attributed to various things ranging from low usage to corrosion to metalurgy variations through the years. I'm curious about something and I'd like some input from the experts.

To what degree does or can oil pressure throughout the engine play a role in this? Oil circulates through the engine galleries under positive pressure created by close tolerances and splash lubricates pistons and cam. Is it be possible that there are restrictions in the spray nozzles and not enough oil is sprayed to the cam for example. The oil pump pushes a certain volume of oil through the system which then is pressurized by restrictions throughout the system. One such restriction is at the spray nozzles. Could it be the case where it's overly restricted due to impurities? As in sludge restricting oil flow? Has this been discussed as a possbility?

[bonal]

Based on another thread showing pictures of the oil pick up screen full of chunks of carbon I think this is a real good question. But short of disassemble is there anything that can be done. We use fuel injector cleaners for this very problem but that's a different issue and an engine can run while the additive is used.

[PTK]

What I'm saying is that if an engine is neglected and oil is not changed as it should how long does it take to sludge up the oil passages and restrict flow? How many "neglect cycles" does it take leaving old oil in the engine for an extended period of time? Could this explain a lot of spalling? I don't think it's metalurgy. If volume is restricted the pressure will drop exponentially. Especially at the squirt nozzles which are restricted to begin with.

I change my oil every 30 hours tops or 3-4 months. I never let it get black. Maybe overkill but I feel good knowing that my engine stays clean inside.

[cnoe]

IIRC there are no "nozzles" that spray-lubricate the cam lobes unless you've opted for one of a couple STC'd mods; they're splash lubricated only. Now the bearings are pressure lubricated but if they are oil starved you'll know it quickly.

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[carusoam]

 

Some ideas to consider.

1) Ney nozzles if you have them...or if they have fallen out, you don't...

2) sludge (agglomeration) builds where flow doesn't exist.  Density of sludge has it settle.

3) Expect that sludge is collecting in the oil pan not growing there.  Some people use a solvent to rinse the oil pan before an oil change.

4) oil coking in the valve guides.  Time and temperature leading to coking and minimal oil flow leads to it not be washed out.

Peter, are these the issues you are thinking about?

Best regards,

-a-

[Mcstealth]

Why can you resurrect in a half hour a Briggs & Stratton engine that sat dormant for 30 years? Why do 70s era motorcycles stay dead unless meticulously rebuilt? How can they find a  60's Chevy in a barn, and drive them away? How can........

I do not believe there will be one particular answer. Yes oil blockage, yes carbon, yes coking, yes metallurgy, yes engineering architecture, yes aliens exist, no aliens don't exist.

I tend to feel owner operation has as much to do with it as anything. I feel temp control is a giant factor. You overheat anything enough times, something, everything will be affected. I re-ringed my two stroke machines after three heat cycles sometimes because the performance was degragaded enought to warrant it. I know how hot they got and could tell I needed rings. 

As for rust on cams and lifter because of non use? I don't know? Why is it that lawn mower engines can be started after 30 years of dormancy?

 

[carusoam]

David,

see if these answer a part of your question...

Cam location and oiling are less than favorable for some engines compared to others.

If a lawn mower is down 15% power would anyone notice.  If the resurrection didn't work does anyone report it.

pulling a cam out of a Chevy 350. Can be done with the block mounted in place.  Owners of barn finds are often looking forward to swapping out a 1 AMU cam... The water pump, radiator and front clip may be in the way of doing it really easily....

A combination of oxidation and wear can cut through the thin layer hardened surface of the airplane's cam exposing the softer layers that really signify the cam lobe's demise.

pulling the cam out can cost more than 5AMU.  Most people are going to feel some pain with a 5AMU surprise.

Hope that helps.

Best regards,

-a-