Don't know if this would work. Never tried it. Z129 has 1/8 inch more stroke than Z120 so compression height should be .125 less, but Z129 has 6.6 compression versus 6.1 for Z120 maybe the .020 difference accounts for compression increase. So if you took off .025 off the top of Z120 pistons you might have 8.1 compression. That might work with good gas. If you run into squish or quench problems I would want not much less than .032 . I have heard of down to .022 quench/ squish but never tried it . I think you will have to flycut the head and I don't know how much you can take out. The only other thing i can think of is cut the top top off Z120 pistons .105. Hope the piston has enough material to cut off. I have no idea if this would work but something to think about. Or make your custom pistons and be done with it.
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