Originally Posted by fast68plymouth
Unless you’re duplicating a known good valve train combo....... big block weight parts, high rocker ratios, Hyd lifters and higher rpm’s can be a challenge to get sorted out.


I agree. We proved to ourselves that the upper rev limit is the lifters. The lower RPM roughness appears to be manifold related. EGT values are all over the map at 2000 rpm but they smooth out at higher revs. The weird pulsing issue was due to the poor fuel rail design and the undersize fuel pressure regulator.