Clacking noise

[zaq123]

wear on the cam lobe nose means wear on the rocker pad that you cant see

you can put that cylinder valves in closed position, pull the retainer clip and slide the rocker to the side enough to take i peek. Little inspection mirror will allow you to see. also as a tip, if rocker wont's slide by hand after the clip is removed, there is a tiny burr created by the clip in the rocker shaft clip groove. Use small piece of 800/1000 grid and your finger to shave the burr a little and the rocker will slide. Will take like 10 finger strokes. Obviously wipe the shaft after and maybe put some paper towel under it... if super paranoid about debris as I am. I noticed that rocker retainer clips and the main shaft retainer clip can create burrs on shafts that keep them from coming out by hand during head disassembly. People proceed with pounding on them which can damaged the shaft. 10 min with a small piece of the fine sand paper in those areas and those shafts slide with no crazy hammering

[I6V8]

wear on the back side of the cam lobe? there should be no wear at all...that's the position when the rocker/valve clearance is present. could be just old and tired valve train. If cam is original, good chance all rockers are too...and springs and valves. Cam doesn't look too bad for that many miles though. My e30 had 150k or something like that and some cam lobes had like 1mm missing

No. Wear on the tip vs none or little on the backside which is where the tappet sits when you check the clearance.

My point was, if you set the lash to 0.010 (or 0.007 at the cam), the (much) more worn tip will cause the effective valve open duration time to be as if you'd set the clearance much looser, for example 0.013 or more on an unworn cam.

I suspect that's exactly what cause my rocker to clank (or clack) this loudly. Plus, it explains why M20s with worn camshafts often sound so much clackier when set to 0.010.

JLevie once mentioned in a post that setting a tighter clearance on brand new hardware can be done. I'd say this episode taught me the opposite. Valve seat wear is accounted for when measuring at the valve stem. Excessive cam lobe tip wear is not. If someone has visible wear in that area and you want to set your lash to compensate for that, you almost need to gradually tighten and then test the play until it runs and sounds right. It's definitely a bit lf of a crap shoot when lobe wear is inconsistent.

digger makes a good point though. If the springs and likely the valves are worn, as well it's best to just get it refreshed completely. I wouldn't have half-assed that if I'd owned the car at the time this was done but assume budget was a limiting factor so not judging too hard.