305 CHEVY REMANUFACTURED CYLINDER HEAD #14101081,Retro.Engineer - Sinclair ZX81 A,ZX81 « RC2014,Hex Head Cap Screw - M10x100mm, Tensile strength 8.8 (25 pcs. Box),Bought untested ZX81 and got a black screen with a working cursor - Sinclair ZX80 / ZX81 / Z88 Forums