[MikeK]

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Originally Posted by 40 Deluxe

MikeK, Are you sure that less than .020" squish height will cause detonation? . . .

40 Deluxe, you have nicely explained the classic squish effect. Based on that, the closer to zero you get, the greater the benefit. But there is another factor, and that's why I said "It is possible. . ." There is a relationship between the surface shape and area of the squish and piston velocity during the actual 'squish'. If you have a large surface area or a long distance to the open combustion chamber there is a pressure buildup in the center of the squish area as the mix tries to escape to the lower pressure open combustion chamber. The squish area of a typical flathead is generally more than twice that of an OHV. The pressure in the center can exceed the detonation point with too small a squish height. What is ideal in an OHV may be too little for a flathead.

If you're really into it, properly placed Singh grooves on the head squish area will help.