A couple of other factors not mentioned yet are altitude and quench. First, altitude. The higher the altitude, the less air there is availible to be pulled in on the intake stroke, and the lower the cranking compression. Hence, the higher the altitude, the higher the calculated dynamic compression ratio (as Moper mentioned) you can get away with. This is definitely a huge factor here in Denver @ 5280' in the city, and up to and over 9000' on some of the mountain passes and I'm not even getting into calculated density! The local dragstrip here, Bandimere Speedway, has an altitude of 5860'! Something that I've seen here a lot is the tendency to overcam based on the static compression ratio and the resulting loss of low end torque and driveability. Nothing quite like trying to build an engine to perform with 20% less oxygen availible than at sea level!
Ok, now quench. This takes into account two factors. One being cylinder head design, the next is piston to head clearance. As dgc333 mentioned, a closed style cylinder head with a flat top piston offers excellent detonation resistance. This is due to "quench", or simpler terms, the area in between the piston and head where the air fuel mixture is squeezed out at high velocity preventing detonation by speeding flame travel. With good forged rods, this "quench" clearance should ideally be set to .040" by selecting the correct installed head gasket thickness in conjunction with measured piston deck clearance. In other words, if your pistons have zero deck clearance, select a head gasket with a .040" installed thickness (with flat top pistons). Go less than this and the pistons will smack the heads at high rpm due to rod stretch, although I have heard of people running .035" piston to head clearance with their engine rev-limited to 5500 rpm. Aluminum rods stretch more, so this clearance must be increased. Keith Black has some excellent information on their web site here
http://www.kb-silvolite.com/article.php?action=read&A_id=35 on quench. You're on the right track by doing your research before you build, rather than having to comprimise later on. Since this is a street car, figure your cruise rpm at highway speed. Check out the Crane Cams website and look at their recommendations for that cruising speed and note the duration specs @ .050". Pick a cam from any manufacturer within 5 degrees of those specs. Note the cam manufacturers compression recomendations, add 1 full point of compression for alumininum heads, or .5 point for iron closed chamber heads with quench set up right, and build your engine around the cam. Spend the extra 6 bucks on a tank of good gas in a well thought out engine combo and you wont be disapointed. :toothy7:
