FWIW, the general rules of thumb I've heard for years re: quench are: 1. .040" is a good target (steel rod motor, not aluminum) 2. < .040" can be better until things like piston rock start to cause piston-to-head collision issues 3. > .050" is where the benefits start to diminish and... 4. at .060"+, you're probably getting no quench benefits
