I know this has been gone over many times but I just need a quick answer. I just got my engine back from machine shop. Had to be balanced as mystery stroker kit was a ripoff. Too far to turn back now. Had roller rocker w pedestal mount on it before rebalancing and after install had exhaust leak from carb. Installed shims during assembly from comp( thick shims). On start up it made hellacious noise from valve covers. Pretty sure I need to use thin shims and noise is from pushrod rocker arm excessive clearance but have not verified. Any body run into this before? I'm new to forum and new to performance motors so any help would really be appreciated.