Blew a head gasket so I figured it was time to put these aluminum gn1 heads on... I also upgraded the cam to a 204/214 flat tappet... got it all together and fired it up and it's super noisy... had 60 pounds of oil pressure... my question is... do I need a different length of pushrod with using gn1 heads? I used stock rocker arms and shafts... I figured if it was the lifters needing to pump up it would have done it by now... thanks for your help