i disassembled two heads last night. one was from a 91 integra ls (usdm b18a1), and the other was from what i was told a jdm honda orthia (jdm b20b). so that is where i am getting my info from. head design: basically the same, newer has marginally larger ports. both are designed to use dual valve springs but don't. valves: exactly the same size on both itake and exhaust sides. (some people say they are different) valve springs: old: progressively wound, exhaust are taller than intake new: linearly wound, exactly the same on both sides, shorterand lighter than the old springs. valve retainers: old: almost twice as thick as the new ones and about a half mm larger in diameter new: thinner and samller diameter cams: i can't measure so we'll belive what people are saying in that the new ones are better. in my project motor i am going to try to combine the good peices off both heads and we'll see what kind of number i can get this thing to have on all oem stuff. i'll try to post numbers later but since i am in wyoming, it will be hard to find a dyno( i don't think there is one in the entire state). but i will do my best and will definately have numbers once project Getto Star is on boost.