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No lubrication for piston

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berks315

New member
Detroit 2-71. Took the air box inspection plate off and number cylinder is bone dry and shiny. The other cylinder is lubricated. Barring over by hand is really hard. Any suggestions why this one is not getting lubed?
 
Well, it could be a few things.

The connecting rods have vertically drilled centers that allow pressurized oil from the rod bearing to spray the underside of the piston crown to help cool the piston.

Some of that oil falls back on the piston "wrist" pin and enters the
grooves in the pin bushings to lube the bushings and pin.

The ends of the pin holes in the piston have seals held in with expansion plugs or "cups" sealing the bushings and pin ends so that the oil is trapped in the bushings and can't flow out to the cylinder walls.

So....
A badly worn rod bearing or a bearing that has become misaligned so that the rod drilling doesn't get sufficient oil might cause this.

Or, a plugged rod drilling or cooling nozzle could cause this.

Or, and probably much more commonly, the piston pin bushing end seal plugs come loose or leak and the lube oil escapes and fails to provide sufficient lubrication. This results in a scored, galled and, eventually, a seizing piston pin.

The problem can often occur not long after installing rods and pistons due to dirty working conditions or the piston pins and end bushing seals are not installed correctly during piston/rod assembly. I have definitely had problems before installing those plugs myself. If you don't catch the mistake immediately, before installing the piston in the block, trouble will quickly occur.

That's why a suction cup and hand vacuum pump is used to verify correct installation after piston/rod mating.

I'm sure there are other reasons but that's what comes to mind.

Engine disassembly is likely necessary to find and correct the cause.

Good luck
 
Ah well,
I'm afraid I completely misunderstood your post. You are describing a dry piston exterior.

Sorry, whiffed on that!

My best guess for that is that either the cylinder wall is being "washed off" by excess fuel and poor combustion from a leaking Injector or, possibly, broken oil control ring allowing oil to enter the combustion chamber rather than being scraped back onto the piston.

It's been a long time since I worked on these so I could be completely wrong.

But....
I do still have my OH manual and this interests me so, when I get a chance, I will try looking up the "splash lube" aspects to see what I might not be remembering.

Does she smoke? If so, what color?
 
Thanks for taking a interest. Unfortunately it does start reliably. Last time I cranked it. White smoke came out the breather tube. Not puffy white exhaust smoke. More like drill bit in metal smoke
 
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Ouch! That looks bad!

I'm not finding much about splash lubrication in my 6, 8, 12 and 16V71 manual other than cam end oiling.
So, I'm wondering if, it being a 2 cylinder engine, they may have lubed those differently?

I've never worked on the smaller model Detroit's so I'm probably just ignorant of something like this one being equipped with "oil slingers" or something similar.

Oil slingers are used in older car and many small engine applications so something like that is a possibility.

And, I do know of instances where oil sllngers weren't put back during a rebuild. I didn't know what they were the first time I saw them.
Was this engine worked on recently?
If so, then that might be a possibility.

I'm afraid that she's going to have to come apart for a new liner/piston kit and be assessed by someone more knowledgeable than me about what's causing this. With all that metal loose, it's not looking good for other components like pump, bearings,.crank and cam either.

I'm sorry I can't be of any help with this one.
 
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