The background for this one is in this thread: https://www.ford-trucks.com/forums/6...rt-1600-a.html

Go ahead and review that thread for insights or ideas, and then look back over here.

There is additional input:

The pistons looked almost brand spanking new, with no stuck rings, clean oil, and they were obviously upgraded "MAHLE" brand rings, pistons, and jugs (which are stouter, and can take more abuse).

The rings were so clean - they popped out from the piston lands about an eighth inch and rode smoothly all around the pistons. In fact - they didn't even look as if they had been worn in good yet.

No damage to the piston upper surfaces, but considerable blackening of the piston tops.

No apparent burning of number three exhaust valve, but it was sooted black from incomplete combustion.
*#3 cylinder was where the oil was coming from

Curb side (#'s 1 and 2) cylinders appeared to be clean burning, with normal ash deposit on valve heads.

No evident cracks or leakage of valves or cylinder to head sealing areas.

Valve stems had less than 0.010 side play (they were tight - like new).

Piston slap: Negligable.

Rod end play: Like a new set of rods and wrist pins.

I think that's about everything, except the stuff I saw right away when I popped the barrels off of the case...

Ready? Make your bets...

Be sure and revue all available info, this one both suprised and disgusted me personally.

 

I have to say piston/s, install not correct, and the skirt was scraping cyl. wall.

 

detergent oil used in a non-detergent motor...

 

That doesn't matter on a new engine, and is good to use to keep an engine clean.
I'm thinking something might have been in the crankcase

 

My vote goes to spark plugs being mis matched only because it is listed twice in the poll. I base this on.........nothing.

 

It does matter on a Bug motor, because it is designed for non detergent oil. Detergent oil keep the crud moving, whereas non detergent oil allows the crud to catch in the areas in the block designed for that to happen... Told to me by my tech school instructor many years ago, who had worked on them, as well as was old enough to have done quite a few, and the newer detergent oils, in a new motor, will kill them. I know of another case, 5000 miles on fresh rebuild running detergent oil, and it failed.

 

Thats what made me think, it cannot be plug related.

 

I can't offer any more clues - but many plugs have manufacturer specific numbers.
That is not a clue



Think about engine dynamics...
What wears most under certain conditions?

 

Detergent oil will also foam up in those motors, which will cut down the lubrication qualities drastically.

HMMM, I might have to change my vote.

 

Hmmm. I've used detergent oil in every air cooled car in my shop for 25+ years and never foams up.

 

That's probably because all oil, detergent and non, have anti-foam additives.
My compressor says specifically to use detergent oil in it.
Detergent suspends the particles in the oil, and clumps them together so the filter can grab them more easily.
It will clean out deposits left by non-detergent oil, and cause issues in an old engine without a filter.
Didn't they start putting filters on the Bug engines in '65, or did that come later?

 

Damn I didn't think you were going to show up! So much for me trying to sound worldly. Many years ago I was told this, and it stuck. Now I know where it stuck. I stand corrected oh master of vw's.

 

Aring installed upside down letting oil push by on the exhaust stroke?

 

The only stock filter - up through 1972 - is a fine screen up under the round plate on the bottom of the crankcase.

It could filter about what the aerator screen in a water faucet is capable of...

 

It's been a while but, wasn't the drain plug magnetized?