This weekend I'll be installing my first valve train in a Flathead, needless to say, I'm looking for as much knowledge and specs about it as I can and going through the process in my head before I take a stab at it. The operation seems pretty standard, as I've been read through a lot of great threads like "Flathead Porting: Soup to Nuts . . . Pictures, Details and Opinions" - by Bored and Stroked. However, I can't seem to find any examples including the 400 jr cam and Zephyr Springs. The other threads and articles have included the Isky Max-1 and the Potvin 3/8 grind, just not the 400 Jr. I know the cams are close to the 400 jr, but I know it has more lift than the others. Everyone says the LZ springs work great, but if you use them with SBC pro-flo valves, you need to shim them, which leads me to my quesion. How much do you need to shim the spring to achieve the adequate installed spring height, and how much pressure are you trying to achieve on the valve; using a 400 Jr Cam, SBC valves and Zephyr Springs?