I retarded my cam using the retard keyway on the timing set I have. By doing this I can maximize the rocker arm ratio 1.73in./1.80ex. I was watching the assembly as I rotated it by hand and noticed that at the beginning of the compression stroke the intake valve is still closing for a little bit. I can imagine, all put together, the engine blowing some of the fuel back out through the intake. Can that be a problem or am I okay? I have a supercharger I plan on using also. This is my first ground up engine build. I'm building a low compression 408w with 2v Cleveland heads.