what caused this?
 

guys, i tore the piston out of the 14 horse today and the walls are smooth as a babies butt, no scratches, pitts, or scores. everything mics out to specs. now my dilema is here in the pics, i hope you can see it. what caused this? the head looks great, other than alot of gook on it. the rings all looked good also. is this piston toast? thanks jeff

That piston is toast. I'd say an overheating or lean condition caused that. Is that the side that faces the valves?

yes, matt, it is the valve side. jeff

I've seen them like that before, and I believe it is caused from carbon buildup.

Never seen it anywhere except the same side as the valves.



Just my 5 cents worth. (I believe the penny should be abolished)

so, i'm guessing that i need to order a new piston? if so, then direct me to the best for the money place to order!!! jeff

The old piston out of my K301 looked very similar to yours. Facing the valves. It had some nasty piston slap/knock, and verticle scoring on the cylinder wall near the valve side corresponding with the piston damage/wear. I checked the rod to crankshaft and it was just out of spec (out of round). But the block did require a .020" overbore. (Had the crank turned too.)

Stens will be $30-$35 or so, OEM probably $150. If you aren't boring it oversize, I probably wouldn't bother with the OEM piston, as you'll probably have to bore it oversize eventually anyway.

Same stuff here.....
 

That looks like what happend to mine as well. I ran the dog snot out of mine pushing snow for a eazy 13hrs. non-stop.:Explode::Explode::HeadScratch::HeeHee: So when someone said overheating, I guess there right, and the fact that it is a '66 k161.One of my winter projects will be to have someone repair it. Was thinking about using my Bridgeport at work if I have to make the cyclender well bigger.

That's exactly how the piston out of my K321 looked.

Just pulled my head to change the leaky gasket. and what do you know my piston looked the same way! (k231) Had a nice little tower of carbon between the valves and cylinder PO must have never cleaned it.