demon carb
Are you running a stock bottom end? If you are then your compression ratio is way off from what they are running. With the components they put together they have good quench and velocity. Your combo is just the opposite with the j-heads, if they are not milled or worked. With the larger runners and Low compression your velocity is probably alot less than running a magnum or 302 head. So I guess I'm saying that I would stick with the 600 for now.