and horizontal faces of the shank 18 and base 19 as shown in fig2 the piston cap 11 with the crushable spacers 14 is then placed in another die and the metallic piston body 13 is cast around the piston cap the crushable spacers prevent the molten metal from contacting the shank 18 and base 19 surfaces where thermal stress could be generated the final fit of the piston cap 11 to the cylinder bore is achieved by lapping or grinding the piston cap 11 to precisely fit the cylinder bore details of the piston cap 11 fabrication include cloth layers comprising the upper crown surface 12 the crown bottom surface 21 and the base upper surface 22 as an example fig7 shows the fiber orientation along a cross section of the crown 12 the carbon cloth is represented by a warp fiber 23 and fill fibers 24 the voids in the cloth layers are filled with the matrix material 25 carbon mat 26 lies under the cloth layers the carbon carbon mat consists of random carbon fiber roving in a carbon matrix fig8 represents an enlargement of the woven cloth fibers the figure is magnified fifty times with the actual length of a side of the figure being 0 07 inch curved warp fibers 23 straight fill fibers 24 and the matrix 25 are all depicted an.