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Piston... MIA

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poolboy

poolboy

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Piston... MIA

The guys over on the Forum where I spend most of my time had never seen anything quite like this. I thought you'd want to take a look, too. The coolant is from removing the head, not contributing to the catastrophe
TR6missingPiston.jpg


I had a leaking needle valve, took the middle carb off, replaced the valve, started the engine;new valve also leaked and flooded the carb; I killed the engine.
I then pulled the fuel line off the middle carb, shot the needle valve with carb cleaner thru the inlet nipple
and restarted the engine.
Within a couple seconds I heard an awful rattle and the engine died.
I restarted, no rattling but running poorly so I shut it down. The noise, the rattling reminded me of a chain saw loosing it's chain.
My thought shifted to the timing chain. I checked the cam timing by comparing the valve lash with the damper marks... Not a problem, so I pulled out the Compression Gauge.
Spark plug #6 looked like this
100_0301.jpg

As to what exactly happened..so far it's all speculation. And I guess really doesn't matter at this point.
Lucky in a way that I have an original, used but un machined, short block to work with.
 
Re: Piston... MIA

Incredible! Have you pulled the pan yet?
 
Re: Piston... MIA

Forgot to ask- how's the head look itself? Did you get a bent valve out of it or more? That sparkplug took a beating.
 
Re: Piston... MIA

Hydraulic lock. Most likely a bent rod, and check the crank for straight and cracks. Have the block magnafluxed, and the bore carefully checked, to make sure you didn't push a wall out.
Remove engine and start over, hope for the best.
 
Re: Piston... MIA

I haven't dropped the pan yet, Randy. I've been working in the engine bay and cockpit.
Probably Wednesday or Thursday I'll clean out the pan.. a day or two before I pull the engine.
The valves look pretty good, I wiped the oil and soot off and I can see where they got peened. It's going to the shop for a better inspection.
100_0291.jpg
 
Re: Piston... MIA

What was the hydraulic part in that cylinder ?
The bore ? The bore... You can imagine what the cylinder walls looks and feels like like
:crazy:
 
Re: Piston... MIA

If you filled it with petrol, and cranke3d it on a compression stroke, it won't compress.........it breaks things. Last item to go was the piston. We don't know what the first one was, but generally, when you hydraulic-lock a cylinder, rod bends, and possibly cylinder wall gets pushed out. Hone it, run a new ring carefully down the wall with the head of the new piston (with no rings) checking every 1/4 to 1/2" for space between ring and wall is a quick check. Not much point in doing a new piston and rings and having to do it all again. Have a machine shop check the rod for straight......if it's bent, it will usually be obvious.
 
Re: Piston... MIA

It's really hard to tell from the one picture, but the rod sure looks bent from this angle. Leaning forward...almost touching the front wall...the angle just doesn't look right for the length of the rod.
 
Re: Piston... MIA

There wasn't an excess of gas in either 5 or 6. The flooding carb was serving 3 & 4.
Honing will not be adequate.
100_0299.jpg
 
Re: Piston... MIA

You see those roughly parallel marks just above the right end of the gudgeon pin? Look like stretch marks? I'd be looking there first. Usually, at idle a piston just doesn't do that. I am thinking you had something in there.....coolant or gas.
 
Re: Piston... MIA

Not coolant..as I said, it spilled when I lfted the head. Head gasket was just fine.
As far as the cylinder walls I can see the gouges and feel them as well. My guess it was because the piston broke and chewed itself up with each stroke, pulling debris into the sump scraping and bouncing against the walls along the way. That was the rattling noise and once it all got dragged below the noise stopped.

Since I have an unmolested short block, I'm really not counting on salvaging anything much from this block.
I've removed the cam followers and if the cam itself looks as good, I'll reuse it.
 
Re: Piston... MIA

As I said earlier, I'd like to see the other cylinders and pistons when you get it apart before passing any judgement. To many unknowns that MAY get answered with a look at the other parts.
 
Re: Piston... MIA

Well, that sucks!

Makes me appreciate the old wet liner TRactor engine though. I once repaired a 4-pot where not only had the piston gone AWOL but the wrist pin went through the cylinder liner. Cleaned up the mess, replaced the rod, new set of liners & bearings plus a new cylinder head (the broken valve head also beat the valve seat to pulp), got it running again without even removing the front apron!

And all that was laying on the ground in the snow. I threw a tarp over the top and stuck a space heater underneath, just so my fingers wouldn't stick to the metal.
 
Re: Piston... MIA

TR3driver said:
And all that was laying on the ground in the snow. I threw a tarp over the top and stuck a space heater underneath, just so my fingers wouldn't stick to the metal.
Click to expand...

And I thought all you guys in sunny SoCal had no idea what the rest of us put up with!!

John
 
Re: Piston... MIA

I didn't always live in CA ...
 
Re: Piston... MIA

Hard to imagine it could disintegrate without even more damage to the head and cylinder walls.

Scott
 
Re: Piston... MIA

Ken, you sure that wasn't ah Audi motor?? :wink:
 
Re: Piston... MIA

If you look under a magnifying glass, I'm sure you'll see more than the low resolution shots here.
 
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