I left the exhaust manifold on the head as the nuts are hard to get at. But now that it's on the bench, I can get a really good look at it and remove it from the head.
My daughter had always complained that this little car was pretty slow, though I didn't think it too bad, but after getting a good look at the top of the pre-cat that's built in to the exhaust manifold I can see part of the problem. It's pretty plugged up. Also there's chunks of the ceramic honeycomb missing, which is often a death knell for an engine as those chunks can get drawn into the engine during reversion pulses.
In contrast, here's the outlet of the pre-cat, it looks like you would expect, but there are some oil spots due to the oil consumption I expect.
And here's what the pistons looks like. On one side the two oil holes are still clear and functional.
But on the other side the holes are plugged solid and not even visible. I tried to clean them out with a dental pic and a mini screwdriver but there was no way that was happening. This stuff is rock solid. You can also seat some piston skirt scuffing, due to the ceramic catalytic converter material getting into the cylinder and also from the occasional low oil level. It's really not as bad as it looks, in that you can barely catch your fingernail on it, and the engine was running smoothly and silently.
Here's what they look like after some cleaning. I gently and lightly use a wire wheel to clean up the sides and tops, then soak them in a gallon of carb cleaner for an hour, then scrape out the grooves with an old piston ring. Last I spray them down with brake cleaner and then scrub every bit of them with hot water, dish soap, and a toothbrush.
Then we go over to the drill press, where I have a little 3d printed piston holding jig, and I drilled out the two original holes to a larger diameter, and added a third hole to each side.
I sure would like to know if it plans on imploding any time soon.
