Excellent video. I can bring the topic into cars and Alfas if you will allow me.
When we send our heads out for resurfacing, I have always wondered exactly what a machine shop was doing with it. I had always imagined a large machine like the one in the video they called a fly-cutter. This appears to be pretty precise.
However, I was also searching some things a couple months ago and came across a few videos where a guy shows how to resurface an aluminum cylinder head with sand paper!! He lays out the sandpaper on the top of a flat surface, like a large pane of glass and then proceeds to drag the head across it with his hands. He periodically turns it over to examine it and shows the high spots getting cut down where as the low spots are still dirty. He keeps going this way until it is all fresh aluminum. Then he switches to finer sand paper to make a better surface. He also periodically uses a flat edge and feeler gauges to check flatness, just like in your video. He explains that the final surface finish depends on the type of gasket being used. Older type engines using a thicker softer gasket don't need as fine a finish as newer engines with thinner gaskets. It all seems logical and in those late Japanese aluminum heads, he has no problem reassembling and running the engine.
So my question is, would anyone do that to our aluminum heads?? Is a complex machine doing a better job than this?
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