'Fly cuts' provide a recess or a pocket in the piston, for the head of the valve. Typical on many engines with high compression piston and/or high lift cams. .
Just an example of fly cut pistons - some only have eyebrows cut in them, some have radically profiled pistons.
Hi Purd: Fly cut Pistons is one of those old terms that stuck from days of yar. A fly Cutter is used to do a lot of Piston rework. But a Fly cutter is not always used or used alone. Different things need to be done to the Pistons depending on Mods to the Engine. For example I just cut some pistons for my friend. I used both a Flycutter a modified End Mill and a Ball End Mill. The Engine had totally Custom ordered Pistons with Different Pin size then Stock and its Deck Hight etc.. It was a Stroker with Aluminum rods.. I had to cut the Pistons for Valve clearance, Deck Hight, Mods to fit the Chamber . They were then cut in under areas to Balance them. Ya its a bunch of work. I am being lazy and instead of including pics Just Google Flycutter MSC or check with some race supply sites. I have dozens of different sharpened HS toolbits to use in my several different Flycutter's to match shapes , angles and Radius's.. If there was interest I could shoot some shots of the next set we do and the differnt tooling and measurments.. Anyway hope this helps. Never take your Cam specs ,clearances , Piston clearances for granted . Measure them.
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