Unlikely but it could be a spun rod bearing. Have you made sure your
oil lines are plumbed correctly? If you're using adjustable rockers arms the nut can come off and loosen the adjustment screw (for FE's anyway). Either way, you want to pull the valve cover to make sure it isn't obvious. The other thing to look for is a cam bolt retainer backing out which would be near the water pump and bumping the front timing cover. Most of these are unlikely but just to consider. And... I'm sorry but my contributions are usually only good for BB motors. Best wishes!